Basically, research WHAT? Opinions?
You got the response here that you will get anywhere - you got them from the people that DEAL WITH IT everyday.
Don't make a point or issue out of it. It's pretty pointless really. It happens, but what can you do when it does?
It happens in EVERYTHING.
If YOU treat everyone the same, and don't go around expecting or fearing pregidice, the problem lies with the OTHER person.