Here to second (or third) this sentiment.
Also to say OP that I did the same last weekend. Just planted a few seeds. The air got uncomfortable fast. but I changed the subject fairly quickly and didn't go back to it. Agree with others that peaking is long and slow, the scales come off in layers, and the cognitive dissonance can be strong / uncomfortable but if you don't force it people will go on their own journey after you set the ball rolling.
The circs were a visit from my oldest friend with her husband. They are thinking of moving to our area (v rural) from London, and he was worrying aloud that the country would be full of right-wingers etc who complain about 'Guardian Readers', and that because he's a bit mouthy he would be bound to end up in argument in the pub. He said something along the lines of, 'For instance around the trans debate, if anyone is anti-trans I'd be bound to get into an argument because I'm pro-trans and wouldn't stay quiet.'
Well he brought it up first, so in I went. Just gently. I said something like 'Hmmm, so do you think that being pro-trans is a left wing standpoint and being anti-trans is right?'
He agreed. I said, 'That's interesting, because until a few years ago I would have thought the same. But now I actually think that the liberal point of view is to protect people from the idea that humans can or should change sex and all the things that fall out from it.'
He said 'but what about people born in the wrong body'
I was able (thanks Mumsnet, thanks GC Twitter, thanks Helen Joyce, KJK, etc etc) to calmly respond. We are our bodies, Cartesian dualism, etc. How could the wrong brain or soul be put into a body?
They both kind of looked away. Then I gently mentioned sports etc - they both agreed that they were against men in women's sports and spaces.
Then I mentioned the social contagion and newness of the concept. Said the idea of trans people didn't really exist before. Friend mentioned her cousin who is gay and v effeminate, gave him as an example of someone from the 70s/80s who was trans. I said kids think in black and white. He might have wished he was a girl. My sister wished she was a boy so she could do all the boys sports etc. But surely they need to be taught there's no wrong way to be a boy and no wrong way to be a girl - not that you need drugs and surgery.
Talked about how it was especially dangerous for children who were being taught by activist teachers that they are born in the wrong body and must be fixed if they don't conform.
Then went back to the right / left wing thing, saying what opened my eyes was noticing that a lot of solid, intelligent, left-leaning people (especially women) I'd seen online were VERY ANGRY and thought, wait a minute, there's something going on here that I'm missing.
My final point - before we moved on to a nice walk and pub lunch - was to ask them if they'd heard of Autogynephilia. He said not. They have now!
I made sure not to bring one more word of it up for the rest of the day, and have been communicating happily ever since without a mention.
But I'd be amazed if they don't percolate, and now have their antennae out just that little bit more for what's really happening.