In a recent Washington Post letter to the editor, a Fredericksburg, Va., man remarked that he’d recently felt “flummoxed by Philadelphia.”

Why? Because “The Post’s Sports section reported on the same day three unseemly acts by its athletes or fans.”

This is a perfect example of a feedback loop of confirmation bias: You have a general impression that Philadelphia sports fans are a uniquely violent and disgusting bunch of louts. The old Veterans Stadium had its own jail! They booed Santa Claus! [Fill in your own cliche. Extra points if you mention cheesesteak.]

Media associated with rival franchises provide anecdotal evidence that confirms this impression. Consumers of these anecdotes come to expect such behavior. The floridly angry general managers of rival franchises stoke controversy about such behavior in order to sell tickets. Eventually you reach a point where someone reads about “three unseemly acts” in the same sports section on the same day.

Are Philly athletes and fans really this bad?

I happened to be at the Nationals-Phillies game in which ex-Phillie/current Nats outfielder Jayson Werth broke his wrist while diving for a ball. “After walking off the field feeling nauseous knowing my wrist was broke and hearing Philly fans yelling ‘You deserve it,’ and, ‘That’s what you get,’ I am motivated to get back quickly and see to it personally those people never walk down Broad Street in celebration again,” Werth told the Post.

Now, this is a bit like Rep. John Lewis having heard the N-word at a Tea Party rally. If that’s what Werth says he heard, I’ll take him at his word. But from where I sat, I heard mostly silence.

What did Jayson Werth think of Philly fans when he was a Phillie? Here’s an example:

You may object that Werth was feeling the competitive heat of a tie ballgame in extra innings. Is it fair to highlight an isolated incident like that?

But this is my point.

I also happened to be at the Phillies-Nationals game, in Philadelphia, where pitching ace Stephen Strasburg sustained the injury that necessitated Tommy John surgery. Philly fans cheered at Strasburg’s exit. “Barbaric!” the sports pundits declared.

But here’s what I remember: After delivering the pitch, Strasburg extended his arm outward, as if to shake off a twinge. To fans in their seats, it barely looked like an injury at all. When the Nats manager and trainer raced to the mound, it became obvious that something might have been wrong. But this was hardly extraordinary: Strasburg was being treated like a Faberge egg during his rookie season. The point is, no one in Citizens Bank Park could possibly have known Strasburg was seriously hurt. And the cheers at his departure could just as easily have been interpreted as cheers of relief: Strasburg had been dominating the Phillies’ lineup that night. Maybe now they had a chance (they didn’t, as it turned out. The Phillies lost that night).

Are there drunken louts at Philadelphia sporting events? Of course there are. But one must account for selection bias here. Should any major city be smeared by the behavior that occurs at sporting events? If so, as former Gov. Ed Rendell notes here, several other American cities should have the reputation that Philly has.

To my knowledge, no Philadelphia sports fan has ever committed anything like the beating of a San Francisco Giants fan outside Dodger Stadium last year.

The anti-Philly brigades need to find a new hobbyhorse.