Racist speech, unless it fits into one of the narrowly drawn exceptions, is protected speech. You could always roll the dice like OU did a few years ago kicking out the racist frat guy and gambling that he wouldn't sue, but this guy seems like he wants a lawsuit. Also, colleges and universities are rightly scared shitless of having SCOTUS or a circuit court of appeals (other than the Ninth Circuit) opine on the constitutionality of campus speech codes.
For several reasons I won't explain here, I don't think it would work to simply expel him, wait to see if he sues, and then reinstate him and assert lack of standing.