I’m 100% a supporter of trans right to use the bathroom of their gender.
There is a reason that bathrooms are separated by gender.
So if you can’t understand why people who don’t believe trans people exist are upset that people are using the wrong restroom, you’re just like the people who can’t understand that trans people exist: it’s a lack of being able to see beyond your own self and understand the position of others. While I strongly disagree with them, their position is not very complicated and easy to understand.