[etanazir]

We seem to have a freedom to choose who we would be employed by; i.e. turn down an offer of employment for moral reasons; say I don't want to work for some animal testing lab.

But say I own a restaurant and a animal testing lab moves to town; now do I have a choice but to serve dinner to the executives of said animal testing lab?

What is the difference?

Per U.S. law; I think you would first need to establish 'sexual orientation' as a protected class like race or gender; to allow people to decide that they don't want to serve people based on some moral judgments but not others.

see http://en.wikipedia.org/wiki/Protected_class