"Discrimination" is more of a negative ideograph than it deserves to be. There are times when what many people would call "discrimination" (particularly "religious discrimination") is actually righteous. The reason is that people choose certain things about themselves (such as their religion), and most choices have a morally better and worse way to make them, and of course treating everyone "equally" is actually wrong if they are morally different. (Instead, we should treat everyone "according to the same rules".) So, for example, if there is a religion you think is evil, it is not just acceptable but actually virtuous for you to refuse to do business with its followers, since ostracism is a valid form of punishment, especially when no other form would be effective or would be punished in turn, eg. by the government (not that ostracism wouldn't be punished by the government).

Note that discrimination against gay people can be validated on the same ground, because although people don't choose who they're attracted to, they do choose who they actually have sex with. Of course, it still needs to be argued separately that having sex with someone of the same gender is immoral.