Tolerance of the intolerant is in itself intolerant.

Additionally, it's not that they don't advocate for gay rights, it's the they actively fight against them. I think this changed very recently, but it has been the case most of their history.

That said, I'm of the mind that most large corps do stuff that is against human rights in one way or another - sweat shop abuse, crushing of labor unions, among many others - and purchasing from Chickfila isn't much different from drinking Coke or buying Nestle. It's part of society. If you avoid corps with rights abuses you must avoid nearly everything.