That is their goal. They want to get Christians fired from their jobs and to shut down their businesses. The legal costs of a small business defending itself against homosexuals is prohibitive. These are not business decisions, these are examples of standing up for principle. And their goal is to put every principled Christian out of business.
The only practical solution might be to make them pay in advance and then make a lousy cake.
"I baked it special"
I think a better alternative is to simply do business quietly by word of mouth or internet.