Because we are social beings, and society depends on cooperation to the fullest extent possible. Denying someone services for something they cannot possibly alter is placing subjective intolerance above objective existence. There is NO objective reason why it should be allowed to occur in a society, it's all a matter of subjectivity. Thus, why not go with the route that provides the best path (not perfect) to harmony? Most businesses do not exist in a vacuum. Most utilize public utilities, facilities and infrastructure and are bound by the same social contract.