Disassociation not always disrespect
Many conflicts in society could be eliminated simply by respecting everyone's right of association- the right to not have anyone imposed upon you. It is about the most fundamental human right there is, and one of the most often violated.
Discrimination isn't automatically a bad thing. I assume you discriminate among the things you eat. A shiny, red apple might be preferred over a ripe banana, and the banana might be chosen before an orange. Everyone has their own criteria and preferences.
This is the reasoning behind the signs in some businesses, which say "We reserve the right to refuse service to anyone". That right doesn't need to be "reserved"; it is always there.
Bakery owners who don't wish to make cakes for gay weddings should never be forced to do so. Other potential customers could then decide whether or not to give their money to the business based upon this information.
Businesses could place "No Guns" signs on their door- so long as they are not incorporated, therefore not in partnership with government and required to operate within limits put in place by the Constitution- to keep away honest people with guns. (No one seriously believes such a sign will stop those who wish to rob or murder, do they?) And those who prefer to do business with companies which don't demand they be defenseless in the face of violent attack can choose to spend their money with shops which actually care more about their customers' safety than about making a dangerous political statement.
If there is a person in town whom you don't like, for any reason or no reason at all, no one should force you to be around that person. You are free to leave the park if they show up, or to cross the street to avoid them. No one should force you to buy from them or sell to them. Just don't complain when the shoe is on the other foot.
If a person refuses to associate with someone because of their skin color, sexual orientation, gender, political beliefs, religious ideology, appearance, odor, spoken language, or any reason at all, they are simply asserting their basic human right. If you disagree with their reason, you are free to speak your mind and refuse to associate with them in return.
Why a business owner would willingly choose to alienate a percentage of his potential customers bewilders me, unless he believes that by doing so he will please even more people who will then flock to spend their money with him. It is possible it could happen.