Funded by the US religious far right...

I agree with Nearlygranny. I would just say I'm not going to discuss it further as we're not going to change each other's minds. He's too far gone at the moment. But possibly you've planted a seed of doubt, and he needs to work it out on his own.

Meh, you cannot prove a negative. He says 'we' are funded by the right? Prove it, and no 'cant find it but saw it' is not proof. I would say the fact that all challenges to this anti-woman nonsense need to be crowdfunded is kind of proof 'we' are funded by noone but individual women tbh. But whatever.

He also sounds kind of sexist, unfortunately. Very women have had it good for a while, they should focus on others now!

I'd be inclined to say to him, quietly,
"I know you've nailed your colours to the mast on this issue now and you probably don't want to back down for half a dozen good reasons, but I actually don't think you're truly convinced. You're too intelligent and there are just too many holes in the argument. But it's OK, we don't have to convince each other, just respect one other. If either of us changes our mind as time goes on and more evidence emerges, I think we should agree to say so, and also agree there will be no 'I told you so,' triumphalism. In the meantime, it's probably wisest if we don't talk about it unless we have learned something new and can substantiate it with hard evidence from an unimpeachable source, OK?"

You could say to him that he is indeed being very kind to respect other peoples identities, such as uni mates and internet people. But why the double standard. Why not respect your viewpoint and accept that maybe his mother has a legitimate concern and is perhaps not actually a bigot full of hate.
Perhaps actually thinking about the question and trying to articulate it would give him pause

@Escapeplanning
That tweets hilarious. How genuinely batshit must you be to think criminals use women's rights crowd funders to launder money.

How anyone takes TRAs seriously is beyond me.

Or ask him what’s in it for women in this new world order?

What exactly... considering the violence and sex imbalances worldwide at the moment - what could be so much worse that women are fighting it?

Ask him to get involved in some charity work that deals with FGM or rescuing girl babies in parts of the world where they are thrown out like rubbish. Get some perspective.

Show him your bank account and promise him a lovely gift when the religious extremist money arrives.
Tell him to not hold his breath waiting.

How about you identify as a teenage boy from now on instead of his mother? You stop taking care of him. I don't think the law would like that very much. Funny how you can opt in to some identities but not opt out of others!

Show him this article.
www.economist.com/united-states/2020/09/03/the-battle-over-trans-athletes-in-american-schools-heats-up
The girls are being funded by a right-wing evangelical group
but only for the court case.

THe picture speaks a thousand words

Yes, he had his shockingly blind spots and the book is a curate's egg, to mix a metaphor or two.

Lot's of mansplaining to the FCA there.

Mmm.

Beware of Berne

Oh, very true. But he's good on sulking...

So it's 'be kind' and 'be nice' unless you feel that someone doesn't deserve you being kind and nice because they have opinions that you don't like and then it's all fine to issue death and rape threats and other violence and abuse, because those women were just asking for it really, weren't they? Loud and clear.

Beware of Berne, or if you must, do make a point of reading his explanation of the 'game' Rapo. He wrote the book in 1964, but to anyone with current awareness of rape culture and CSE, it is a hair-raising read or an InCel textbook, depending on your viewpoint. Especially with reference to 'girls under the age of consent' aka children...

Assuming he's not actually going through some genuine crisis of faith, this sounds very much like a form of sulking. In which case there is no point whatsoever in engaging with it directly. It will stop when he makes a rational decision to stop it.

Take a more oblique approach. Start reading Eric Berne's "Games people play" slightly ostentatiously, and make a point of leaving it around open at interesting places.

I assume he also thinks that human sexual dimorphism isn't real? Ask him if he thinks this is true for all placental mammals, or only for humans? Do non human animals which reproduce sexually have genders, or do those species have a male and a female? If they have a sex but not a gender then why does he think its different for human animals? He'll probably tell you something factually incorrect about people with DSDs at that point. Remind him that non human animals also have DSDs.

Or, just repeat the phrase "women's rights are not yours to give away. It's not my job to educate you out of your male privaledge. This conversation is not accepting new answers and has now been locked by an administartor".

Lastly I'd encourage him to start watching the YouTube channel "Telltale" which is run by an ex cult member who dissects different movements according to the BITE modal to see if they qualify as cults. He hasn't done one on TRAs but the parallels are so unbelievably clear that he might just start joining a few dots. Also recommend The Atheist Experience on YouTube as a good debate show between theists and atheists. The TRA arguments are almost verbatum the same as a lot of the arguments for theism (not surprisingly because it's a dualism based belief system) and anyone who is even passingly familiar with formal logic should be able to easily recognise this. Neither of these channels have anything to do with trans issues and you should absolutely suggest them to him in a neutral unrelated way just as something he may find interesting. But it might just get a bit of joined up thinking going on so that next time he's parroting his TRA nonsense a little voice in his head starts going "that sounds like circular reasoning/appeal to authority/thought stopping clichés" etc. Ultimately the belief in "gender" is only a half step above 6 day creationism, flat earth theory, and the people who think an archangel helped them find their car keys, but sadly a lot of people also believe in that stuff. So I've no great hope that society at large will have the collective intelligence to reject this latest strain of anti science nonsense any time soon.

I wouldn't enter the conversation with him. He believes what he wants to believe.

I'd ask him this - if he had a little girl, does he think she should be able to use a woman's changing room, toilet or vulnerable space without being exposed to an adult penis?

If he says no to that, then I'd be very worried indeed.

Do you have any pets...?😈

Antibles I like your approach!

OP - what does your son's girlfriend have to say?

Short, not shirt! 🙄

I enjoyed pulling my 'woke' DS up shirt the other day when he made a throwaway comment about someone being too attractive to look 'like a lesbian'.

"I'd have thought a woke bro like you wouldn't be making assumptions and accepting offensive stereotypes like that."

He backtracked instantly. Most satisfying. Since he called me T*RF, boomer and Karen all in the same conversation within two or three breaths recently, I will not hesitate to challenge his pronoun use and gender assumptions as suggested by Antibles until he grows thoroughly weary of it!