That viewpoint, in itself, is at least partially cultural.

Yes, there are other means of oppression; people can be oppressed for having the wrong sort of noses, or living on the wrong side of the river, or coming from the wrong family. These I see as seperate, though related problems; resolving the issue of race will do nothing directly about the other problems (and may even throw them into sharper relief), but I don't think it's a good idea to refuse to solve one problem just because others might still exist.