Individuals are individuals. Sub-cultural mores are products (distortions) of the media. The two are not the same. However, the latter seems to have tremendous power in framing public debate.
Not that everyone in a group identifies with every assumption of that group, but these things are more complex than simply being shaped by the all powerful media.
This notion itself is becoming more nebulous with the rise of social media. Traditional media has lost much of its power, and much of that power has been taken over by social media. When the media merges with and to a large extent becomes us, what happens? I'm not so sure.
Your reply supports this: whether they do or don't (and to what degree) is an individual matter. I wasn't disputing that experience can change a person's attachment to racism.
At the same time you will find people going against type regularly. Which has a moderating effect. It's hard to think X are bums when you see hard working people from X.
I also often see people complain about their own ethic group a lot, though this is more about class than race.
Pretending groups are somehow above criticism is more about manners than fact.
PS: I have watched several people become more and sometimes less racist after moving to DC. This has far more about cultural friction than the people involved.