This poster campaign run by www.mecasa.org is principally aimed at students in Maine, USA, although it has spread more widely. The small print reads “Realize words have an impact - even if you don’t see it. Challenge sexist and homophobic language. Choose different words. Change the subject. Support people who are being harassed. Use humor to change minds. Violent words support violence.”
It must have been very difficult to word the posters. They need to be sufficiently direct to make the point, but not cause offence in themselves. I reckon they got it right and am pleased to support the campaign with this post.