While this thread remains open I'll give a perspective on this stuff worth every penny you're paying for it.
Stereotypes exist for a reason, otherwise they wouldn't be stereotypes would they? The problem with that is our human brains are pretty much stereotype machines and we tend to sort people into stereotypes without even thinking about it. We'd be foolish to ignore our instincts- to ignore the stereotypes completely because, as I said, they do exist for a reason. You can use these ideas to anticipate what someone might do and think about strategies to deal with it(or capitalize on it I suppose) ahead of time. That said, it's equally foolish not to mention terribly unfair to assume someone will fit into your stereotype before getting to know them. It pretty much makes you the first 3 letters in the word assume...
In the past couple of years it sure seems like the number of people from both sides of the political spectrum ASSuming things is at an all time high, especially on the internet. Everyone is so mad and blaming everyone else for every problem under the sun. I know we've got problems but we live in a nice country. We're pretty safe, we oppose discrimination, we're relatively wealth compared to the world. No it's not perfect, yes we should work to improve it, and yes we have different ideas of where to go from here. But we're in a good place. Smile, go outside. Have some drinks, fly, whatever and stop worrying about everyone else and their opinions and biases.