It's ridiculous.

The baker didn't refuse service because they were gay. He refused to make a gay-themed wedding cake (a product he didn't produce), and offered to make them a traditional wedding cake instead. They then spun this into "being discriminated against" and sued. He's being sued for not producing something that he didn't offer.

Think rationally about that.

You don't walk into a donut shop and demand them to make you a pizza. They don't offer that. But you're gay, and their refusal to give you a pizza is apparently discrimination. Sue them.

Or perhaps you want to hire an actor to be in a film you're making to show your partner on your wedding night. You go to a well known local actor. He's happy to be a part of a wedding film, and says he loves doing wedding movies when he gets the chance. Then, you reveal to him that the film requires unprotected sex with another guy. He apologizes, but says that this would violate his beliefs, and that he must decline this particular script. He says he would gladly act in a film that doesn't include unprotected sex with guys, and recommends several alternatives, but you won't have any of it. You sue him for refusing you service based on your sexuality. You win in court, and now all actors are legally required to do ANYTHING they are told to do while the camera is rolling. You can no longer refuse roles. If someone wants you in a video, and you call yourself an actor, you MUST do it. Refusal would now be discrimination.

Then you go to a local artist who does portraits. You demand a gory painting of dead babies and murdered puppies. The artist says he will gladly paint a portrait of someone, but something that gruesome is against his beliefs and not something he offers. Wait a minute... you're gay and he just denied you service. Sue him. FORCE him to paint what you want, despite that it was against their beliefs. This is just another case of discrimination.

Look, I agree- if the baker said "I'm not selling you a cake because you're gay", that'd be wrong. That's not what happened though. He refused to make a gay themed wedding cake; he didn't refuse to make them a wedding cake.