THE MOST galling part of the letter outlining the decision to remove from view a student painting at the center of a congressional controversy is not the claim by the architect of the Capitol to have undertaken a dispassionate review. It’s not even when he says the artwork doesn’t comply with House rules. It’s when he says he looks forward to working with all participating members of Congress for the next, upcoming 2017 Congressional Art Competition.

Really? Why bother?

It is pretty clear that the student-artist’s work was sacrificed to political pressure and vigilante censorship — in the U.S. Capitol of all places. That should alarm anyone who thinks the First Amendment, unlike art, is not a matter of personal taste and choice.

At issue is “Untitled #1,” a painting by Missouri student David Pulphus that depicts racial confrontation with police. It won unanimous approval in the Congressional Art Competition in Missouri’s 1st Congressional District last May and, like the more than 400 other entries accepted and approved, was displayed in the U.S. Capitol. For more than six months, the painting hung in the underground tunnel between the Capitol and the Cannon House Office Building and was viewed by thousands of visitors without incident.

That changed when an alt-right blog and other conservative commentators started a campaign against it, objecting to its imaging of police as animals. Congressional Republicans got in the act, taking it upon themselves to remove it from the wall and give it to Rep. William Lacy Clay (D-Mo.), who, in turn, joined with other members of the Congressional Black Caucus to have it rehung. Architect of the Capitol Stephen T. Ayers ordered the artwork removed on Tuesday, saying it violates House rules that include a prohibition on subjects of contemporary political controversy. If that determination had been made when the painting was first reviewed (and approved), it might have carried some credibility. But other paintings can be seen as dealing with political themes, and the architect’s revelation came only after a mean-spirited political campaign, and after House Speaker Paul D. Ryan (R-Wis.) weighed in with his own review (“Disgusting”). That sequence of events sets a sad precedent.

The painting was returned to Mr. Clay, who said he will display it in his office. Young Mr. Pulphus, for his part, has acted with restraint and dignity. His only comment: “The art speaks for itself.” So does the unseemly stampede in Mr. Ryan’s House.