NOW THAT the Boston Red Sox have announced a lifetime ban on a fan who made a racist remark at Fenway Park the other night, how about if every team in Major League Baseball — and other American sports leagues —follows suit by enforcing a similar policy? That would send a loud message, at last, that expressions of racial hatred are off-limits even in the raucous environs of sports arenas.

Groups that track hate crimes — against Jews, Muslims, African Americans and other minorities — report an upswing in incidents across the nation, including at houses of worship, at cemeteries and on college campuses. And while there is no data tracking racial taunts specifically in sporting venues, Fenway Park has long been notorious among African American players, who say fans there are the most racially hostile in big-league baseball.

On Monday, Baltimore Orioles center fielder Adam Jones, a five-time All-Star, broke what amounted to black players’ stoicism on the subject, describing publicly that he had been subjected that day to abusive fans who called him the n-word and threw a bag of peanuts at him. The next day, Fenway fans loudly cheered Mr. Jones, a nice gesture and fitting repudiation of the abuse he had suffered.

No sooner had that happened, however, when a Red Sox fan in the grandstand, Calvin Hennick, attending the game with his mixed-race young son and black father-in-law, reported a separate incident involving a lout in a neighboring seat who directed a racial slur at a Kenyan woman who had just sung the national anthem. When Mr. Hennick asked the man to repeat the remark, he did, whereupon Mr. Hennick reported the incident to an usher.

The team’s response — evicting the racist and banning him permanently from Fenway — was forceful and swift. In Boston, a sports-crazy city with a fraught racial history — the Red Sox were the last major league team to field a black player — the club’s sanctified civic status gives its pronouncements special weight. It is only a pity that it took Mr. Jones’s courageous public remarks, after 11 years in the league, to trigger the right response. A veteran African American pitcher for the Yankees, CC Sabathia, confirmed what has been widely known for years: “You get called names, n-word, all kinds of stuff when you go to Boston. We know. There’s 62 of us [black players in MLB] and we all know. When you go to Boston, expect it.”

Black athletes shouldn’t have to expect it. The Red Sox are seeing to that, and Major League Baseball officials are reviewing security protocols at other big-league parks. If incidents persist, MLB officials should adopt a true zero-tolerance policy, as European soccer leagues have done in the case of teams whose fans have engaged in racial taunts or violence, by imposing a temporary ban on fans. If a team plays to an empty arena for a few days, that should drive home the point that the ballpark is not an anything-goes zone.