This is just guys talking~ Chances are only one of them is really transphobic but the rest are joking and agreeing because they don't want to be seen as gay.
I knew some guys once that were making gay jokes. One leader. I wasn't part of it. Until the gay guy in the class was like, "Oh, my boyfriend would find that hilarious!"
They all stopped, thought about it. laughed a second and one was like "Dude, Im sorry". It was awesome.