Why people assumed because I'm wearing a ski mask that I will rob people?

Why are people so prejudice. I always had a fascination with ski masks I have a regular one a couple of octopus ones. I mean everyone started screaming as soon as I entered the mall and as soon as I entered Walmart everyone started running and screaming most people in wal mart look like crimials what's so different about me, how am I standing out from everyone else? I'm really sad.