I'd still think it's awful because I don't see being gay as a bad or immoral thing - there's pretty much no imaginable situation in which allowing gay people to exist unhindered causes damage to anyone. I'd suggest that if being gay were a conscious choice, the shop should have a right to refuse service to gay people, but again, I'd have a right to stand outside their shop with placards, shout about it in the news, etc etc.

On the other hand, allowing neo-nazis to go unhindered may quite reasonably result in people's deaths, so.