Hiring a person to perform in front of a crowd of hundreds/thousands of people is not the same thing as hiring a person to make a cake.

Your example would be better if the gay couple had asked this baker to cater the wedding or serve the cake himself at the wedding.  But they didnt.  All they asked was for him to make the exact same wedding cake he had made for hundreds of straight couple before.  And he refused.

When you open up a business in America, you agree to run that business fairly and equally and treat all customers the same.  This guy is using his religion as a way to discriminate against someone who he does not agree with - which is exactly what these laws are put in place to protect, and why no lower court has sided with the baker.