He has recently given backing to Education for All, a campaign against homophobia in schools by the gay rights organisation Stonewall. Last month, it put up posters on 600 billboards across the UK bearing the giant slogan: "Some people are gay. Get over it!"
Mr Barrowman said: "Join me and help exterminate homophobia. Be bold. Be brave. Be a buddy, not a bully." Stonewall reports that the reaction to the campaign has been "overwhelmingly positive".
However, one graffiti artist in Blackburn refused to "get over it", scrawling "NO" on the poster.
And on Teesside, even parts of the gay community objected.
James Wood, an actor and sexual health worker who came out aged 17, told a local newspaper he had never been bullied at school for his sexuality. "The posters are too confrontational," he said. "They won't do gay people any favours.
"The type of people who are not gay friendly are not suddenly going to look at the posters and think 'I won't go out gay-bashing, I'll sit in and listen to Kylie'."