Tweeting to her 74,000 followers, Hannah Jane Parkinson said that the headline had "irresponsible word choices", and was just another in a long line that stigmatised or trivialised mental health conditions.
Warner was quick to respond to Parkinson's comments, saying he's "not sure why anyone would think it derogatory of mentally ill."
At which point, MP Douglas Carswell got involved in the online row.
Parkinson continued to fight her corner on the way that mental health is reported in the media.
She also called out other media organisations who have insensitively reported on mental health in the past.
Warner, who is an associate editor at the Telegraph, later apologised for his headline later saying that it was obviously offensive if so many people thought so.
The headline has since been changed to 'Corbyn has just appointed a man from cloud cuckoo land as Shadow Chancellor'.
Parkinson chronicled her argument on Storify, writing: "[I] went on a tweet storm after the latest irresponsible use of language around mental health (this time in the Telegraph, but not limited to that paper by any means).
"It's really important that mainstream media pay attention to the impact language around mental health and illness has."