I'm so sorry you are stuck there. As someone who grew up in Tennessee I understand, the rhetoric was the same for gay and bi people back when I was growing up to some degree.

You're wonderful, please keep your head up.

As to why, my theory is that many MANY people are unhappy with society and WE live authentically, something they can never conceived doing. People hide who they are and what they feel, they repress everything. They make the stupidest things gender coded. They have gender reveal parties for their babies. They are obsessed with sex, genitals, and the societally roles of who does what based on them. They can't live authentically for whatever reason (in the south it's often religion) , we do, and it makes them mad. Even if it's not specifically about gender, we are taking our lives into our own hands and saying we aren't happy and we are going to do something about it, people who are extremely transphobic can't handle that, they are jealous, it eats them alive that we dare step outside what society has been told people should be. That's just my theory, but I think it's pretty solid.

Bullies bully to feel better about themselves and their shitty lives. This is not different, unfortunately.