Why do people I don't know call me a b****?

Ok only 2 people ever called me a ***** but they were random people who I don't know who I just walk by on the streets. Like this one time I got out of the bus and this homeless man who I don't even recognize started yelling at me and calling me a *****, then he almost got aggressive but I ran to someone for help. Then last Saturday I was taking the bus with my friend to Hollywood and this man stepped into the bus and when he passed by my seat he started spitting out "stupid *****" at me. I'm so baffled. Why do these people call me a ***** without even knowing me. It's like I don't even have a sign tacked to my forehead with the word ***** on it. Why are people like this?