It is his business and he can have it open or closed on sundays, he can offer only Kosher food or not, he can feed biblical values to his employees who are free to stay or leave. And he can take the profits of his business and do with the money what he wishes. But when he says that he wants to impose his religion on this country and he gives millions to organizations which exist in large part to attempt to deny gay persons the right to marry in civil (not religious) ceremonies then he becomes a fair target for economic boycott as were the owners of lunch counters in the 60's who refused to serve Blacks, when it was still legal to do so. I am sorry to so often hear those on the right scream about Sharia law and the need to keep Islamic rules from over taking the American law, but seem to not see how the attempt to impose a particular version of their own faith on all of us is just the same problem using a different hammer.
Does anyone seriously believe that Catholics should be able to outlaw divorce and birth control, that Jews should be able to stop the sale of bacon, that traditional Mormans should be able to make us all polygamists, or that fundamentalists should be able to tell us who can marry whom based on their interpretation of a line in their 3000 year old book? It was those same fundimentalists who made the laws that made it illegal for a white person to marry a black person, based on that same 3000 year old book. To me these are all the same imposition of a religious rule on a nation where we don't all share the same belief system.