I'm open about being GC, but I don't volunteer those views and wait for them to come up. Like /u/Boozebabe, I try not to get angry or show anger, as unfair as it is, since people tend to not listen when a vaginaperson gets angry. I'm lucky I was never really part of a feminist scene or even an LGBT scene IRL, so I don't have as much to lose. The people I know that are pro-trans are definitely in the camp of not being particularly interested in queer politics and just having a knee-jerk reaction to an issue they've given almost no thought about.

I don't make the mean jokes that I do here to let off steam, since only people in GC circles would understand that they come from a place of utter frustration and being sick of misogyny, the sacred cow of man-feelings and the erasure of women. Anyone else would just hear, "transphobe!" and stop listening.

One thing that's worked for me: Pointing out the transing of kids, and what's really happening behind the scenes of those positive propaganda pieces. Most people outside queer theory circles are sensible enough that, even though they mostly support transgenderism, they can see that gender dysphoric kids obviously should wait until they're adults to access hormonal treatments and surgery. Pointing out all the things the transkids propaganda articles don't tell them, especially the permanent sterilisation of transed children, is damning as hell, especially since the pro-trans side tries so hard to cover it up. Such things may make parents think, what else are they not telling me?

It always helps to suggest things in a way that plant a seed of mistrust in the trans public face and encourage people to research things themselves. Generally, they've been fed a steady diet of propaganda and honestly don't know any better. They (like me, once) are very sympathic towards transgenders, who they see as always being dysphoric and always desiring SRS, and they see recognising their gender conversion as harmless. I've pointed out, using examples, some ways that it's not harmless that busts those misconceptions to good effect. In particular, the bathroom bullshit, and how erasing the definition of female opens the door to anyone, not just transgenders, who is a man wanting to get in the women's and girls' changerooms and showers, with the establishment being powerless to stop him if he claims genderfeels (regardless of what he looks like), again using examples.

Another technique is to not make your point outright but allow the other person to connect the dots. Eg. pointing out how harmful gender stereotypes are; a lot people know that gender stereotyped socialisation of kids is BS, and most people were gender nonconforming in some way as kids, so it may make people think twice to consider that if they were born very recently, their normal behaviour would be pathologised, with the adults in their life deciding to suddenly refer to them as the opposite sex and gender conversion therapy prescribed.