I don't understand your "difference" between being forced to provide service in a restaurant and being forced to bake a cake.  To those who owned and worked in the segregated restaurants, they were, indeed, being forced by civil rights laws to serve those they did not believe should be eating with white folks.  

I think the laws that keep the public market places open to all are very important laws.  Perhaps I think that because I grew up in one of those Southern states while and where segregation was an accepted way of life; and remnants of that attitude still exist.  Everyone agreed on it in times past - all the white butchers, bakers, and candlestick makers agreed that they would not sell to blacks or only sell to them out the back door.  Social pressure to conform can be as bad as it can be good.  

Do we want the Christian version of Sharia or can there be a common ground where people of different beliefs can respect each other and share space to buy and sell goods?