It doesn't say he refuses to serve gay customers, just that he refuses to make wedding cakes for them. I think that's a necessary nuance, would you call it discrimination if a Muslim owned restaurant refused to prepare pork but would still serve you otherwise?
The decision to abstain from pork preparation is not customer-discriminatory in the way a baker refusing to decorate a cake for a same-sex couple is.
That's a good point, I don't see what bringing the government into it is supposed to accomplish though. Outside of turning "I won't make the wedding cake because you're a same sex couple" into "I won't make the wedding cake because I'm fully booked". In the first scenario the business can be boycotted and can be put out of business for not treating their customers fairly, in the second no one still gets any cake.