That's not exactly what the pizza joint in Indiana said. They said they would have no problem serving gays in their restaurant, but would not cater a same sex marriage. Boy, did that stir up a shit storm!

Should a business be able to choose with whom they want to do business? Let's take religion out of this entirely. Let's say they are straight up bigots. Let's say the policy is "Gays make us uncomfortable, so we won't serve them here". They would lose the business of the lgbt community. Word would get out that it is a bigoted pizza place. Business would further drop as people that didn't want to be associate with bigots stop going there.

Would gay people still be able to find a pizza. Damn right they would. They would go to the place across town, and so would their friends and family. What if there were no other pizza place? My bet is that the sandwich shop around the corner would see that as a market opportunity and add pizza to the menu.

In today's world, allowing a business to discriminate freely would only result in self-segregation. Bigots segregated from everyone else.

The second issue here is force.
In this case, we are are asking the government to force a bigot to serve pizza against his will.
The bigot is not forcing anyone to do anything.

In a perfectly free world, no person would be forced to do anything, or be allowed to force another person to do anything. All interactions would have to me mutually agreed upon.
Of course that is a utopian ideal and cannot work. There HAS to be an authority to enforce the non-aggression. That authority would have the ultimate monopoly on force. Our government has that authority. All laws and regulations require compliance ultimately under threat of violence from the authorities. We should be careful about how we ask them to use that power.

My position is that the government should only be allowed to use force, to prevent the coercion of one of it's citizens.