Remember when "British soccer hooligans" was a punch line?

There really wasn't anything funny about the violence. Maybe it was the distance that allowed us to poke fun — the distance and the novelty of people losing all sense of proportion over a game.

Well, there's no longer any novelty to sports violence in the Bay Area.

Two years ago, we shared the shock and revulsion when Bryan Stow, a paramedic from Santa Cruz, was beaten savagely in the stadium parking lot after a baseball game between the Giants and Dodgers in Los Angeles.

Today, we mourn with the family and friends of Jonathan Denver, a 24-year-old Fort Bragg man who was stabbed to death a few blocks from AT&T park after attending a Giants-Dodgers game on Wednesday in San Francisco.

Stow, who suffered brain injuries, was assaulted because he wore a Giants cap in Dodger territory. It appears that Denver was killed for wearing Dodgers' gear in Giants' territory. Two men are in custody, and police are looking for two others.

Colors? Territory? These are words we usually associate with street gangs. But their thuggish behavior isn't any more reprehensible than the antics of overzealous fans who fight and maim and even kill over their allegiance to blue, orange and black or some other team's colors.

"While this is one of the most storied rivalries in baseball ... nobody's life should be at stake whether they are at the game, leaving the game, whether it's six blocks away," San Francisco police Chief Greg Suhr said Thursday.

It would be bad enough if this senseless violence occurred only at Giants and Dodgers games. But Denver and Stow are only the most tragic examples of a growing trend.

If you've been in a stadium recently, you've seen the signs and heard the pregame announcements explaining how to summon security.

Along with the stories about Sunday's football game between the 49ers and the Indianapolis Colts, news services filed reports about more violence at Candlestick Park, where stadium security was beefed up after two shootings at a preseason game in 2011.

Unruly behavior isn't limited to professional sports. In June, police broke up a brawl at a semi-pro football game in Rohnert Park. In July, Cotati police were on hand after a Little League playoff game, though tensions on the field and in the stands didn't boil over that day.

Recounting Wednesday's events, Suhr said Denver, his father, his brother and one or two other companions encountered a group leaving a nightclub near the stadium. They argued about the Giants and Dodgers and went their separate ways. When they crossed paths a couple of blocks away, they fought, and Denver was killed.

Fans responded when Bryan Stow was attacked — denouncing violence and donating money to defray his ongoing medical costs. There may be an opportunity to do the same in this case, but no sum of money can bring Denver back to his family.

Most fans want to see athletes compete, not to pick fights. More fans need to remember these are not wars, and when the game ends, brawling isn't going to change the score.