You mention “unease” at the end, and you suggest that your own “discomfort” — the discomfort involved in talking to the acquaintance or to your friends about this situation, I assume — might have led you to underestimate the risks here. In doing so, you’re admitting that you’re not sure how safe it is to be around him.

Even if you’re correct that the man poses no danger to your friends, there are other reasons to tell them about your experience with him. He did something awful. In deciding whether to associate with people in our personal lives, information of this sort is one thing we reasonably take into account. Because these women are your friends, you are right to care about whether they are associating with someone they might choose to avoid if they knew what you knew. To withhold the information is to not live up to the demands of friendship.

My daughter’s preteen friend was hanging out with us one day recently. She casually brought up the following story: She was at the mall with her older sister, her stepmother and her father, who is a police officer. In the child’s words, a “fight broke out between two huge black guys.” She said they were punching each other in front of a store. The stepmother asked the father, who is white, to go over to them and show them his badge even though he was off duty. But the father did not step in.

Police were eventually called, and so was an ambulance, and according to the girl, there was “blood everywhere.” I cannot figure out what is right. Should the man have stepped in? Or should he absolutely not have intervened because he was off duty and with his family? Does this story seem contingent upon race? What is the role of a trained professional in a crisis situation like this? Name Withheld

Because this officer was off duty, he had no obligations beyond those of any other citizen. But police officers generally treat as worthy of professional respect a concern for maintaining the peace even when they’re not on the job. It’s part of their code of honor. So off-duty officers (like any citizen) can reasonably decide to involve themselves where there’s a decent chance they can help and there’s no moral or legal bar to doing so. Given that police officers have practice in breaking up fights, this man would probably have done a better job than the average citizen. If he had thought waving his badge would help, he could have done that too, as the child’s stepmother suggested. And that would not have necessitated “bringing them in” or otherwise entangling the combatants with the justice system.

How does the fact that the two brawlers were black affect the situation? We’ve become attuned to problems of overpolicing, but as the journalist Jill Leovy has observed, underpolicing — “too little application of the law” — may play a role in the violence that plagues swaths of urban black America. Was the officer less moved to intervene because the combatants were black?

But there’s another way that this circumstance could have factored in. Owing to the distressing salience of race in everyday interactions between strangers in this country, an intervention by a white off-duty police officer might have escalated things more than the intervention of a black one. And a uniformed officer of any race who had specifically been called to intervene would probably have been less of a provocation.

For that reason, it might have made sense not to intervene — especially when the fellow had family to protect — and to call the local police instead (although mall security should already have done so). However you do the calculations, though, he was certainly entitled to have remained on the sidelines.