The gun store owner said the guy was belligerent. And that his FFL license could be revoked if he knowingly allowed a belligerent person on the gun range. The US government (ATF), he claimed, specifically states that he is never supposed to allow anyone on the gun range that he has suspicions about. So I side with the gun store owner.
I saw an incident a few years ago in a gun store that was similarly interesting. It was on a Saturday morning, and the gun store was crowded and noisy. There was a man who looked and talked as though he was from the middle east talking with the gun store owner about buying a handgun. I was close enough to hear most of the conversation, before the customer was thrown out of the store. The customer was told there was a waiting period on handgun purchases. The customer started saying how that was stupid and he didn't like it. And his voice got a bit loud. The gun store owner thought the customer was mad at him. So he raised his voice, and the conversation continued and became an argument, and the customer was thrown out of the store.
About half way through the conversation, I realized that the customer was not arguing with the store owner at all; he was sympathizing with him about how stupid (in his opinion) handgun waiting times are. Yet his accent was heavy, and he did raise his voice, and the gun store owner (and others) misunderstood. Yet it's human to sometimes misunderstand, and the gun store owner did what he thought was necessary to diffuse what truly seemed to be a bad situation about to get worse. He threw the customer out of the store, rather unceremoniously.
So, should that customer have felt racially or religiously discriminated against?