On one hand you have a businessman refusing to sell someone his services because he disagrees with how they live their life. Nobody is asking him to condone gay marriage, participate in the service, or even approve of it. Just take money, and cook food and serve it.
On the other hand someone has been told they wont be served because of the way they live their life. They weren't told they couldn't live that way, it's a one off incident, not a systemic problem (although some very awful people are portraying it that way), and they can get food at any number of other places. Instead of going elsewhere, they're throwing a huge fit and insisting on being served out of spite towards the person doesn't agree with them.
If anyone I ever knew acted like either of these people, I'd slap them in the face and tell them to grow the eff up.