>Does a chinese family moving into an italian neighborhood all of a sudden mean that no one can open an italian restaurant?

No. It does mean a lot of other things though, like a vastly increased chance of chinese/italian intermarriage for their descendants, which means their descendants will not share your ethnic identity - it will be destroyed. Whether you think that's a good or a bad thing is an entirely different matter.

>the only reason you would not want to live near someone else, is because you (not you personally, in the general sense) don't like that someone else.

Not liking someone is not the same as not wanting your descendants to be like them. Wanting for yourself (or, your group) is not the same as hatred of everyone else.