Off course it's common. That doesn't make it right though. I don't know how you can argue that disliking someone because of eye color, race, sexual orientation, ... is alright.
The rest of your post has the smell of a relativism argument. You can call someones upbringing an extenuating circumstances when talking about someones attitude or character. But at a certain point in your life most people are smart and mature enough to see when their views are hateful, or racist, or deeply annoying, or sexist, or egoistic, or... and you can fault them for holding on to those things. That's also what why the word "(im)mature" is being thrown around a lot in this thread. It's more difficult to fault little kids for using hateful words, because most of the time they don't know the weight and meaning behind those words. An adult however can, so if he continues using them, all you can say is that they're acting very immature.