You’re right, and it doesn’t to me either, and I feel that it’s wrong, and I wouldn’t go and get a cake made with someone I know does this. I also think that you and I would agree on more than not. I’ll also add that I don’t have a dog in the religion debate here. But I still feel very strongly that in a free society it is their right not not be compelled to write something which directly contradicts their belief. I’ll need to think about this more in general, I might end up changing my mind on it, but at least for right now the right to not have to say something you don’t believe feels important to me. Let me ask you this, if an atheist baker were asked to write “Jesus is Lord” on a cake and said no, would you take issue with that? I wouldn’t; I’d argue that is a very clean first amendment right, and an important part of living in a liberal society. I also would go as far as to say that isn’t even intolerance from the atheist, it’s simply them believing something.
To your second point, while I agree that a business owner should not discriminate against a particular demographic, I’m not sure I’d go all out on any time someone says this they’re discriminating. Every religion and value system has prohibitions, and few of them are aligned. It’s possible to respectfully decline to do something as it directly contradicts your beliefs. Now if your beliefs are discriminatory, that’s a different and more complex question entirely. I’m not sure what to think about that case.