Although the guy who made that comment to Eric did not use the most polite choice of words, he had a legitimate reason to raise the question. It would have been more appropriate for him to offer his business card while apologizing for being personal and saying "Perhaps you were assaulted or in a fight. I run a boxing gym if you would like to learn how to defend yourself." He could have been giving someone an opportunity to do something about a situation they did not have the courage or incentive to address. This is far different from the person who would ask a stranger the first part of his remarks.