Back when I was knee-high to a leisure suit, kids like me from Bridgton had to know two things:

1) Don’t go wading in Stevens Brook;

2) Don’t wear blue and gold in Windham.

Windham and Lake Region were fierce rivals back in the 1970s. Being on the Lake Region side, we always heard rumors about some Windham ruffians hurling rocks at one of our buses that had stopped at McDonald’s on the way back from a game in Gorham, or how a bunch of Windham troublemakers challenged some Laker fans who were minding their own business to a fight in the parking lot after a basketball game.

Who knows if any of it was true? There was certainly always tension whenever the two schools met on the field or court, but it didn’t escalate beyond that when I was in high school, and the rivalry eventually died when Windham moved up to Class A. Thank goodness because now the folks from Lake Region can stop in Windham and eat their Big Macs in peace.

Most rivalries come and go (don’t let anybody tell you over the next couple of weeks the Celtics and Knicks have a long-standing rivalry. The last time it mattered was 1984). A few endure. Bruins/Canadiens is among the few that has stood for generations, and they’re back at it again in the Stanley Cup playoffs.

Habs vs. B’s was the most anticipated matchup of the postseason, not just because of the long-standing history, but because the rivalry reached new heights this winter with the Max Pacioretty/Zdeno Chara incident. Montreal fans demanded Chara face charges for checking Pacioretty into a turnbuckle, breaking one of his vertebra. A criminal investigation by Montreal police remains open.

Dodgers/Giants has moved from one end of the continent to the other and remains one of the most intense rivalries in sports. So intense, in fact, that Bryan Stow, a 42-year old Giants fan, now lies in a medically induced coma because a couple of unidentified Dodger fans beat him up in a Dodger Stadium parking lot after the season-opener between the two teams.

Violence among players and fans and even between players and fans often defines rivalries. Any time the history of the Red Sox/Yankees rivalry is reviewed on television, you can pretty much count on seeing Pedro Martinez flinging Don Zimmer to the ground or Lou Piniella slamming into Carlton Fisk at home plate and igniting a bench-clearing melee that ended with Graig Nettles trying to make Bill Lee’s left shoulder his right shoulder.

Blood and broken bones send fans into a frenzy and give all of us in the media something to talk about for days and weeks. It leads Sportscenter, even without any rivalry underpinnings.

When the hostilities have a history behind them, any major dust-up instantly become a touchstone of the rivalry, with the footage dug up any time the combatants meet or have another scuffle and everyone waxing nostalgic about the battle like it was Ali vs. Frazier.

But what happened to Stow, a father of two, brought the Dodgers/Giants rivalry ‘a step closer to the soccer hooliganism for which we scold Europe and South America.

While most of America expressed shock and outrage, one Pittsburgh-area columnist who wondered what Stow was thinking wearing a Giants jersey in Dodger Stadium. Apparently, he was, at worst, wrong and, at best, foolish for supporting his team and got what was coming to him, according to this idiot.

I think we’d all be surprised and a little disturbed by how many fans agree with that premise. Take a survey in the Fenway or Yankee Stadium bleachers any time the Sox and Yankees are playing each other. I bet the split between those that agree and disagree would be pretty close and probably greatly influenced by whether the survey was conducted in the first or seventh inning.

It is absurd that a Red Sox fan can’t go into the Yankee Stadium bleachers or someone wearing pinstripes can’t enjoy a game at Fenway without having beer poured on them or obscenities hurled their way.

It is even more ridiculous that security and ownership know this type of stuff goes on and look the other way. Yet somehow, we’re shocked when it carries over into a parking lot after the game?

It seems too much to ask fans to let the rivalry play out on the field, court or ice and leave it there. A lot of them take their rivalries personally, a little too personally.

So security is beefed up and alcohol sales are curbed to keep the louts from acting up, but these measures are usually a) taken only after an incident gets the media’s attention, and b) temporary.

The Dodgers stepped up security after a 2005 incident. They did it again just two years ago when a fan was stabbed at an opening day game against the Giants. In light of the latest incident, they’re debating whether the police presence at the stadium should be uniformed or plain-clothed.

It shouldn’t take a franchise merger in the spirit of Jay and Livermore Falls high schools to get Dodgers and Giants fans and Red Sox and Yankee fans to co-exist peacefully. It also shouldn’t take a death at a game.

The enmity may be fueled by alcohol or on-the-field belligerence and cooled by police presence or zero tolerance policies. Ultimately, it’s on each individual fan to know when it stops being an intense rivalry and starts becoming too personal.