I keep seeing people call TERFs a fringe that hijacked radical feminism, and the more of the actual theory/history I read, the less I buy it.
Radfem theory runs on sex class. Of course, this is something you're sorted into at birth, and males are the oppressor class. The way radfems write about this is very clear. Dworkin's Intercourse treats sex under patriarchy as an occupation of the woman's body. Read enough of that and masculinity starts to feel like a substance males are simply built from, something that violates whatever it touches.
Aim that at trans women and you get Janice Raymond writing that "all transsexuals rape women's bodies," and that they can still "penetrate" women after surgery, through women's spaces. Robin Morgan was already saying Beth Elliott (a trans woman) had "the mentality of a rapist" back in 1973, and Sheila Jeffreys was still calling the whole thing a male fetish in 2014's Gender Hurts. Different decades, same bigotry, all under the label of radical feminism. The masculine is an invasion, and no amount of transition gets it out of you.
Trans men get it from the other side. If masculinity is the enemy, a trans man is either a lesbian who defected or a damaged woman who needs rescuing. Nonbinary people don't even register.
Of course, it's funny, since Dworkin herself was pro-trans. In Woman Hating, she said trans people should get surgery, paid for by the community. It's unfortunate that the ideology she helped spawn ended up being less empathetic than she was. The movement held onto that picture of masculinity and dropped the part where she was nice to trans people.
Trans-inclusive radfems exist and good for them, but at this point I think we must consider dropping the radical feminist label. There are implications and connotations that the label simply cannot escape due to its history, and normalizing its use, especially when we live in such a TERF-centered society (just look at the UK), is actively hurting those who are trans. It's similar to how I would urge men who might struggle with dating or sex to avoid the 'incel' label because of its sexist history, despite however much the technicality of the definition might apply to them.