Sexuality (last i checked) wasn't a protected class yet, it should be, and it should be federally, but it isn't, so in this case there really isn't anything to due.
I absolutely morally disagree with not serving them, and if the courts decide that they were illegally denying service, well probably see a suite of changes to the laws. But, as we've seen with other cases related to this issue, i don't see that happening.