Why do people hurt transgender people?

I think that a lot of us are stuck in the gender box, trying to meet the expectations of being female or male and never quite managing. I think this creates a lot of pain in a lot of people. Trans people have the courage to get outside of the gender box they were born into. That creates fear and resentment among those who are also unhappy in their assigned gender, but have never thought of getting out of it or haven't had the courage to.