I don't like the question. Asking "Is Mormonism racist?" is too broad.
If Mormonism is (by definition) racist, then all Mormons are racist. That's obviously not true. So I'd have to say, No, Mormonism is not racist. But I know what issues you're trying to address, and I don't think you'll be satisfied with that answer.
One of my many objections to Christianity is that almost every Christian denomination has institutionalized homophobia/heterosexism. That means that most Christians voluntarily belong to organizations with homophobic and heterosexist teachings and policies, and therefore I don't think it's far off to say that most Christians consider homophobia and heterosexism valid positions. However, it doesn't mean that every Christian is a homophobe or heterosexist, or that Christianity is by definition homophobic or heterosexist.
It might make more sense to ask:
1) Does the Mormon Church have a history of racist teachings and policies? Yes. That's true of many white-majority U.S. Protestant denominations, and even of some that aren't white-majority.
2) Does the Mormon Church presently have racist teachings and policies?
Not that I know of, but I guess it's open to discussion.
3) Was Joseph Smith a racist? No comment.
4) Was Brigham Young a racist?
No comment.
But the question as phrased makes it impossible to discuss the issue of Mormon racism without painting every Mormon as a racist, and I don't think people of good will are going to be too eager to do that.