Racism is a cliche problem. It's a cliche because it really just doesn't go away. But there is a misconception as to what it really is. Most believe that one group of people just automatically begins to hate another and that they are evil. Since things can turn violent then the people doing these actions must be very bad people.
But the reality is a little more complicated. Racism stems from fear. People who are racist are afraid of those people who are not like them. It's all fine when there is only one different person, it's like 'oh this person is from so and so'. Even if its just 10 people then its usually fine. But the problem begins to manifest when the numbers become significant, say when an entire population moves in.
Suddenly these strange people are a noticeable force and they moved in to your land. It's like some strange guy moving in to your house, the one you lived in with the people you know for the last 10 years. Suddenly this new guy comes and he's brought his friends. You're house is big but you can't say no because its a public house (example).
Now these guys need to eat. So they open your fridge and start to help themselves. You don't like that very much. After all they're not one of your kind. Then they might even begin to intermingle with the people you know and this makes you uncomfortable. One guy might want to marry your sister. There's nothing wrong with the guy but you get a strange uncomfortable feeling. You'd prefer it just didn't happen because it'd be much simpler and you'd rather just not go there.
You're not a bad person, but you just don't like these foreigners that much and worst of all they have no intention of leaving. At first it was ok, they didn't interfere, but now they're changing the decor to match their tastes and getting more and more vocal in the house. You don't like that at all after all its your house!
The funny thing is, the house always belonged to you in the past, and no matter how many generations of the newcomers live in it, you feel it still belongs to your people. After all... they were here first.
The feelings of resentment are there, like some baby brother you now have to share your toys with. But the worst part is having to share without someone you don't really know that well and you don't identify with.
Just imagine that I come to your house and stay there. You never invited me and now you have to share all your stuff with me. I have a job and I contribute fairly and all, but still I can help myself to things that you never really owned, but when others take them you feel jealousy. Worst of all I'm here to stay whether you like it or not. I dunno... I get the feeling you wouldn't like me very much.