The Scottish Secretary and his Tory MSP son have condemned a "homophobic" tweet from a well-known pro-independence blogger.
David Mundell became the first openly gay Conservative Cabinet secretary when he came out in January 2015.
But after his son Oliver, the Conservative MSP for Dumfriesshire, addressed the Scottish Conservative conference on Friday, the Wings Over Scotland website tweeted: "Oliver Mundell is the sort of public speaker that makes you wish his dad had embraced his homosexuality sooner."
The blogger insisted later that the tweet was "Toryphobic" rather than homophobic.
But the Scottish Secretary said: "This sort of behaviour has to be called out. We're not going to face down homophobia unless we call out people who practice it."
The Conservative MP also reacted on Twitter, saying: "@NicolaSturgeon asks 'What kind of country do we want to live in?' My answer: not one where homophobia is acceptable."
His son, who was elected to the Scottish Parliament last May, branded the Wings Over Scotland comment "absolutely disgusting and unacceptable".
He said: "I get a lot of abuse online. There are certain individuals you don't want to give oxygen to but sometimes comments people make just cross the line.
"For other families who have gone through similar situations, comments like that make it more difficult for people to be who they are.
"I don't think that's the kind of Scotland anyone wants to live in."
While he said the Wings Over Scotland site "is not officially linked to the SNP", he insisted there is "more they can do to clamp down on this sort of thing".
The MSP continued: "It is really important they call out this kind of behaviour. There are lots of reasonable people within the independence movement. But there are still some unpleasant figures who get given airtime by senior people within the SNP.
"This is an individual who has interacted with SNP MSPs and MPs, and distributed material in the last independence campaign. There is duty for all of us in politics to call out those within their own ranks who are offensive and unpleasant."
Meanwhile, David Mundell has told how he was "immensely proud" when his son was elected to the Scottish Parliament.
In his speech to the Scottish Conservative conference in Glasgow, the MP said: "I remember so well taking my own seat in Parliament 18 years ago, when you were all of nine years old and you were there with us on the opening day of Parliament, on July 1 1999 - and it fills me with pride to watch you now speak so eloquently and effectively on the floor of the Scottish Parliament.
"And you've won us both the niche accolade of being Scotland's first ever father and son pair to be elected to Holyrood - and the bonus to me is that some people don't know which way round it is."