Is my stepmom a good parent????????

I'm 18 & going to college, but I still live with my dad & stepmom. I commute back & forth to school. Ok here's what happened. The other night, I came into the kitchen, & my little brothers started messing with me. They're 12 & 13. They called me a loser because I didn't have any friends or a girlfriend. They said I would become a serial killer one day. So I told them to shut up & leave me alone. Then my stepmom overheard us, & she started yelling at me. She told me to leave my brothers alone & that I was an ***hole. So I tried explaining to her that they were messing with me, so I was defending myself. She said that I was in her house & that if I didn't go to my room, she would kick me out. I told her that it's not her house. She doesn't work & it's my dad's house. Then she made me leave. So I'm 18 & I understand it's legal for her to do that, but was it really fair? My dad told me to just keep my mouth shut for now on. My stepmom even admitted that she was wrong for calling me an ***hole, but my dad says that I still disrespected her. I had nowhere to go. I spent the night at my boss's gym. I had a key to the gym because he let's me workout when I want. But was this really fair? Am I the bad guy here? I'm not feeling sorry for myself, but COME ON MAN! lol