On right of refusal (in this case I'll be focusing on businesses)
I definitely think they should be allowed to refuse to serve whomever they like for whatever reason they like. That's their problem. If they don't want to serve me, they're the ones losing a customer, not me. If they don't want to serve gay people, or Muslims, or Native Americans, then let them. They're a private business after all, aren't they? And in doing so, they lose paying customers who are in one of these groups they refuse or who take issue with them refusing certain people groups
TL;DR
Refusing gay people service is bad for business, but they should be allowed to do it anyways