When he says he's not.
Abusive men spend a lot of time and energy denying their abuse of their victim/survivor. It is crucial to them that they never admit what they did or are doing to a woman. It is partly important because they know they can't stop doing it. It is critical that they deny it so that they don't have to face it; get arrested for it; spend their lives paying for it. Like the woman they abused does.
Coercive Control became an offence in December 2016. One of the first men prosecuted was in September 2016. The crucial phrase in this report is "he denies everything". http://www.telegraph.co.uk/news/2016/09/09/man-24-is-one-of-the-first-people-jailed-for-coercive-control-of/
The Duluth model of power and control places "denial and minimising" of behaviour as central to the abuser's tactics. http://www.thehotline.org/2013/08/taking-a-spin-around-the-power-and-control-wheel/
An abusive man will see evidence of his abuse and he will simply pretend he cannot see it. It can be written down in a list and he will look at it with anger and incredulity. His memory is wiped clean the second he wipes his fist it seems. He will look around at broken furniture and assume a tornado swept through. He will see a woman crying and cowering before him and assume she is hormonal and having a "moment" to gather herself. Or she is too sensitive. Or she has been "washing dirty linen in public" and it came back to bother her. Or she tripped and fell into her deep misery all by herself.
Men who abuse women are skilled at tactics of minimising and denying their abusive behaviour. It allows them to continue. Women already made vulnerable and unsteady by abusive tactics believe them. Women who have left abusive men have a wry smile at the nonsense lies they continue to tell themselves and others. Women yet to come into their lives will believe them unfortunately. Until it is too late.
Denying abuse is central to coercive control. Dr Kate Cook wrote about this for The Huffington Post recently. She also comments on the fact that only 65 cases of coercive control led to police action in the first 6 months and 11 police forces recorded no crime at all. Men will continue to find it easy to deny this abuse if prosecution is rare. https://www.huffingtonpost.co.uk/dr-kate-cook/monitoring-coercive-contr_b_13227720.html
Women's Aid, The Freedom Programme, Refuge and most organisations working with victim/survivors acknowledge "denial and minimising" as a key tactic of domestic abusers. https://www.womensaid.org.uk/information-support/what-is-domestic-abuse/recognising-domestic-abuse/
In action this is how it frequently works. This is some of what an abusive man may often tell anyone who will listen. Mainly other men but often women too. They will of course tell this to their next woman target. At a pub bar somewhere, as he leans against it thrusting out his crotch, he will charm his slightly inebriated and utterly gullible audience. He will say that he really did nothing at all. That she made his life a misery. That the constant nagging got him down and pushed him to the brink of depression and suicide. That she was lazy. That she was always flirting with or sleeping with other men. That she never had sex with him and that made him feel worthless. That she spent all his money and he worked himself to the bone to keep a roof over her head. That she was a bad mother who neglected the children. That the children hate her. That her friends all think she is mad and have nothing to do with her. That even her family abandoned her. That she was cruel to him. That she hit him. That she called him names. That she deliberately did things to make him angry. That she is a liar.
Men in that bar will believe him. They may buy him a pint and empathise. They may criticise the woman vocally. They may help him to send horrible texts to her. They are fools who fall for an abuser's act. They collude. An abuser is good at getting others to collude in his abuse. Women coming into his life will want to be better than that awful woman. They will want to heal him after the misery and pain she caused him. New victims cannot be blamed for an abusive man's behaviour. Women should not blame women in this situation. They are all victims of the abuser.
Let me offer you an alternative side of his bar story. Possibly she frequently asked him to stop doing things which hurt her physically or emotionally. This was not "nagging". He may have threatened suicide to make her stay or he used depression as an excuse for his behaviour towards her. She never stopped cleaning and cooking because he ensured she knew that it was her duty. It was never quite good enough and calling her lazy made her try even harder to service his needs. She probably did not sleep with other men and was afraid to look at one or have men as friends.
In reality he could have been jealous and possessive and constantly accusing her of infidelity until it was too exhausting to negotiate time away from him. She stopped going out or socialising. She was frequently bullied into sex she didn't want. She may have been forced to perform sexual acts that she didn't like. She may have been raped. She may have been forced to watch porn or encouraged to look like the women in porn. She thought there was something wrong with her for not liking sex. She rarely thought it might be because he made her feel so dehumanised that intimacy with him was repulsive. She relied on him financially as he had prevented her from working, perhaps kept her pregnant in order to make her give up work. He may have prevented her from bettering herself with study and so hindered her chances of ever being able to live independently of him. He made her feel guilty for the money he provided. He made her feel like a servant or prostitute. He would often call her this. She was unable to properly care for her children as he affected her mental health. Or she did care for them very well despite being in a situation where doing so put her at risk of harm. She might have considered getting help, but he would threaten her that social services would take her children away. He may have had sex with her in front of the children in order to degrade her. He will consider her to blame for this. The children might resent her for not leaving him sooner and not protecting them. It is a normal reaction. Children with trauma from domestic abuse sometimes side with the abuser. His behaviour has left them with mental health issues too. They are overly anxious, underachieve at school, have eating disorders, struggle to form healthy social attachments, have low self esteem. Etc etc. The traumatic effects of his behaviour on his own children are heart-breaking and devastating. Her friends were excluded gradually from her life so he can make up anything he likes about them. Likewise her family.
She was "cruel" to him. She left him or threw him out. She was kind to herself when she did this though. She did call him names he didn't like. She called him a bully, an abuser, a perpetrator of domestic violence, a liar, a headworker, a rapist and a bad father. He won't like those words. She deliberately made him angry when she left him. She deliberately made herself safer and happier.
So now take a look at the man at the bar, or the man on Twitter, or the man joining a men's rights group to shout about justice for men. See that man through the eyes of the woman who left him. Sift his words for the alternative. Ask yourself what you know to be true.
A woman left that man. She may have left him bitter and angry. But she left him. I suggest you think about why. I suggest you move further down the bar as an absolute minimum. He is an abuser and if you buy him a pint, you are a colluder with abuse.
To my particular abuser, who did many but not all of the things above, I say this. Every time I say sorry for no reason. That's on you. Every time I flinch at a raised voice. That's on you. Every time I wake sweating from a nightmare of what you did. That's on you. Every time I cry remembering the things you did and said. That's on you. Every time I double lock the doors and then check them again. That's on you. Every time my child struggles with self esteem. That's on you. Every time my child suffers anxiety around adults. That's on you. Every time my child flinches at a raised voice. That's on you. Your abuse is yours. Own it.
The deep joy I feel every day when I wake up and look at the sky, it is a sky full of freedom and hope, that is nothing to do with my abuser. I did that with the help of women and an inner strength I didn't know I had.
A real problem of all of this behaviour is that some of these men go on to kill the women they abuse. As we saw just yesterday a woman was stabbed to death in front of her children and the man police suspected to kill her then went on to kill himself. http://www.independent.co.uk/news/uk/crime/two-children-watch-mother-stabbed-death-murder-suicide-hertfordshire-police-cheshunt-a7589441.html
It is often argued that "women kill men too though" when research shows that overwhelmingly it is other men who kill men and overwhelmingly it is men who kill women and they do so frequently in a situation where they are the intimate partner of family member of that woman. A recently released report by Professor Sylvia Walby the chair of UNESCO in Gender, Violence and Society provides research which shows that of the 437,000 global intentional homicides per year 95% have a male perpetrator. Two-thirds of the victims are women. 50% of the global intentional homicides of women are by an intimate partner or family member. These are frightening figures from robust research data. https://oapen.org/search?identifier=623150 Uk Office For National Statistics data shows that of all homicides, 44% of female victims were killed by an intimate partner as opposed to only 6% of males. https://www.ons.gov.uk/peoplepopulationandcommunity/crimeandjustice/compendium/focusonviolentcrimeandsexualoffences/yearendingmarch2015/chapter2homicide
So in answer to the question "when is an abuser not an abuser?" When he faces and deals with his own abuse. Or dies.