As a private business, I don't see why he can't ban people because of their astrological sign, their bad taste in pizza, or any other thing other than membership in a protected class.

The tax exemption shouldn't exist at all, and the states in the surrounding area should make an interstate compact to put an end to that nonsense by imposing minimum tax burdens for sports teams based on total revenue. The amount of tax avoidance (by some of the most profitable companies in the country) made possible by playing one place against another is crazy.