People like to size up a person by the way that they look or act. For example, I have even seen TV shows mention this, a person who is disabled in some way is immediately considered a good person. Disabled people do not do things wrong they think. I can tell you that's a lie. All my teachers in school learned that.
Sure, some people decide to stick to the stereotypes. It's their prerogative. But never assume that any person, no matter what they look or sound like, is any 1 specific way.
Take me for example. People who don't know me very well would see somebody who was relatively white has one arm and lives in the suburbs. They would probably assume that I do not know very much about life, that I am Republican, and a very nice person. And they would be wrong. I am a mixture of almost all races, I am only missing half an arm it does not affect me being good or bad, and though I live in the suburbs I have also been on the streets before 2. I know how that goes. Also I am NOT Republican or Democrat. Personally I hate the government and thank people are stupid for fighting on one side of the other instead of against the government completely. Team red team blue ...both suck.
Point is you don't know a person from a min or two of sizing them up. Well ...most do not. I have met people who are capable of doing that pretty well. But it is a very rare gift that most people do not have. Although I am sure more people think they have it then actually do. Trust me when I say most people are not capable of doing that. So it is best to assume that you do not know that person and give them the chance to be the person who they really are.
Let them tell you who they are.