This is a really helpful discussion.
It hadn't occurred to me in this context (of course it occurs to me in other contexts all the time, e.g. Corbynites' and the Labour left's blind spot for antisemitism), that there are well-meaning people on the left who are simply unaware of the horseshoe theory, and don't realise that just because someone opposes the far left, that doesn't mean they're far right; in fact it may just as well mean they oppose authoritarianism on both the left AND the right.
But that's quite a grown-up political viewpoint - being a moderate probably seems like a cop-out when you're young and ignorant. It takes maturity and a good knowledge of history to realise that Stalin isn't the opposite of Hitler, but just a slightly different flavour of murderous authoritarian dictator.
So to be give the young and ignorant the benefit of the doubt, maybe some of them genuinely do think that GC feminists must be aligned with the Christian right. Because they lack the knowledge of history or political philosophy to realise that they themselves are actually the ones with the regressive, authoritarian views.
I always forget how little history many young people are familiar with. I had assumed gender extremists saying this were just trying to attack feminists. But maybe they are just more ill-educated than I gave them credit for...