You also seem to be assuming it is not possible that income inequality might be one important cause of racial division.
According to Robert Putnam, all else held equal, racial diversity causes social tension. If causing social tension is a valid argument against something, this should be an argument against racial diversity.
http://archive.boston.com/news/globe/ideas/articles/2007/08/...
http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9477.2007.... (sadly it's paywalled)
So we are faced with the following choices: a) you can oppose racial diversity AND inequality because both cause social tension, b) you can oppose neither (for this reason, at least), or c) you can be logically inconsistent and therefore incorrect about something.
I choose (b). What do you choose?
Although I'd prefer to call it "argumentum ad assume racism"
My argument is a -> b, a -> c, c is false therefore a must be false, and the argument for b is also flawed.
Premise 1: X causes social tension is a reason for us to oppose X.
Fact: Racial diversity causes social tension.
Premise 2: The person I'm arguing against doesn't believe racial diversity should be opposed.
Conclusion: Maybe Premise 1 is wrong. But then using premise 1 as an argument against inequality is also wrong.