Do not give what is holy to the dogs; nor cast your pearls before swine (Matthew 7:6)
(I'm not saying your friends are swine, just that it's better to not speak to those who won't listen)
I think this could apply in cases like this. I think the verse means to be sensitive to what your audience is ready for. I still find it troubling that someone that knows your are Christian to promote such evil without a reaction on your part. They might be testing you. If anyone tried to win me over for gay rights they would hear my stance on that right quickly.

