“Go get cake elsewhere”
is not a consideration in the case.
You,want to say they are jerks for suing for their rights? Super. That is not a consideration. 
All you are doing is whining. 

How is the baker participating in the wedding? No baker participated in my wedding.

What if only one of the gays showed up and orderedthe wedding cake? What if the guy who showed up was marrying a man named Kim. The gay man orders an elaborate, custom wedding cake that has says on it, “Congratulations on your Wedding, John and Kim.”

The baker would not refuse to do that because he would not know it was for a gay wedding.
Is the baker going to go to hell?

The problem is the baker is a really bad Christian and has weird beliefs.
Religion religion is not an excuse to discriminate.