I believe you are more likely to be mugged by a white person because there are more white people in the US. Adjusting for population, you are more likely to be mugged by a black man than a white man. However, this is because being mugged is directly tied into how poor the mugger is. White men tend to have more money than black men (due to racism and having blacks catch up to established wealth in white people).
My grandfather was very racism. He would give us some money (a small amount since he was still living in the Depression era view of money) and tell us to watch out for black pickpockets. We would say that we will only let white people pickpocket us.
But my grandfather was missing on what to watch out for. He should have warned us about poor people (not many white collar muggers out there).
Another problem is that humans tend to overuse anecdotal evidence. Like statistics will say one thing, but that is ignored because of a personal story. When seatbelt laws came out, many people would argue that they heard of one story where if a person had been wearing a seatbelt, they would have died. They completely ignored all the other cases where people lived due to seatbelts because those stories were not really out there.
Some sterotypes I have are
1. People hooked on certain drugs will likely steal from family and friends.
2. Personal drama lessens as a person matures and ages.
3. Poor people on the street are most likely to ignore me. If they do interact, it is to panhandle. It is rare to be mugged.
4. If walking the streets at night, muggers are more likely to stay in poorly lit areas away from crowds. Pickpockets and theives are more likely in very crowded places.
There are probably many more.