How in the hell are you supposed to determine that anyway? If you own a cake shop do you make all your customers sign an affidavit that they're straight? Force them to reveal the gender of their spouse?
And that's why YOUR side of the argument loses. These laws won't result in "No gays allowed" signs, because, unlike with race, you can't just look at someone and tell if he's gay. All these laws will result in are things like some bakeries run by very religious individuals not make cakes for same-sex marriages. Which is perfectly fine, because other bakeries will, so no one gets hurt.
Do you really think it's alright to force a deeply religious baker to make a cake for a gay wedding if the baker is devoutly religious and thinks he's helping the people to sin? Yes, the baker is wrong-headed and should change his mind, but people aren't perfect, attitudes take a long time, sometimes a generation or two, to change. You'd be causing the baker significant emotional distress. Probably, the baker would shut down and get a different job. And what you get in return for harming that baker is that gay couples wanting to marry don't have to type in "gay friendly bakery near Memphis, TN" once in their lives.
This isn't like racial segregation. There are superficial similarities, but this isn't going to end with gay-only schools and gay-only hospitals and gay-only restaurants. Such a system would be impossible to enforce, and very few people really would want to do that anyway: gays have already been tolerated in Western society for a very long time, since before slavery was eliminated even.
This isn't about hate. It's about religious freedom. You just think the people who will exercising their religious freedom are stupid and wrong, so you don't want them to be able to exercise it. They are wrong, and likely stupid for some value of stupid. So are the people exercising their freedom of speech to deny the Holocaust. But you don't lose your freedom of speech for being stupid and wrong, and you don't lose your freedom of religion, either.