There are some people who are homophobic, but not transphobic (which sometimes leads them to doing pressuring gay people to transition, so they're not gay). Don't think it common in the US, but it happens.

a lot of parents don't even know how they will react themselves until it happens. my mum had christian brainworms and was all "it's a sin! eternal damnation will await you!" blah blah whatever. but after i came out she was all "a loving god wouldn't condemn my child to hell for being a removed"

I assumed my mom would have tried to be more supportive when I first realized I was trans (until my brother brought a trans boyfriend home...) and I assumed my step-mom would have been more disapproving (even if I assumed she wouldn't express it much directly).

By the time I actually came out though, I suspected the biggest problem I'd have is I'd have to deal with my mom's dysphoria (egg?), and that turned out more true than I even expected.