There are many reasons for why women cannot be priests–but the basic one is that God made it that way.
If you have ever read the book “Women priests and other fantasies”, by… hmm… can’t exactly remember the author’s name, but it is Micelli, or something close to that. Anyway, his chapter on “women priests” is a wonderful explanation of why men are priests, and women are not.
But the idea that it is “racist” (I think you mean sexist) is clearly out of whack. Men and women are equal because we are all created by God with souls. We are by no means the *same*. Even in a physical sense this is obviously true. I don’t think anyone claims the NBA is sexist for not allowing women to play. Heh.