Why are most people so mean to autistic people like me?

I don’t understand why my family is so hard on me. They seemed more hard and stern with me than everyone else. Nobody wanted to be my friend in elementary school or middle (accept for my two best friends) because I was ugly, weird and I was huge for my age. At age 12 I was already 5’10.
I get mocked for my height, big feet and I’ve been used as a punching bag all my life. My aunt yells at me a lot more than her other nieces and she’s so HARD on me and always on me about stuff. I get she loves me to death but I don’t like her sometimes. I get yelled at the most!