Last Thursday heralded the dawn of the 2011 baseball season and, with it, the reconvening of arguably the most storied and bitter rivalry in professional sports. This year’s first confrontation between the San Francisco Giants and Los Angeles Dodgers, however, was marked more by what happened in Dodger Stadium’s parking lot than on its field.

As if to add insult to injury to the first of three losses to the Giants’ arch-rivals in the season-opening four-game series, two Dodgers fans blindsided and savagely beat a fan wearing Giants gear after the game, hospitalizing him and causing permanent damage to his head. Forty-two-year-old Bryan Stow of Santa Cruz is currently in a medically induced coma and has had part of his skull removed to account for swelling in his brain.

The backlash has been significant: The Los Angeles City Council, the Dodger Organization and the Giants, among others, are offering a total of $100,000 in rewards for any information on the attackers, and Stow’s family is accepting donations to offset his rising medical costs.

As one of the worst attacks on a fan in the recent history between the teams, such violence to a member of the Giants fan base is no doubt inflammatory enough to prompt comparable brutality in retaliation the first time the Dodgers and their fans set foot in AT&T Park.

It makes sense; loyalty to one’s team is one of the guiding principles in baseball, and retaliation against offending opponents has always been one of the checks and balances among players dating back to the days of Christy Mathewson and Mordecai “Three Finger” Brown, when brawls on and off the field were common and a “proper” lady wouldn’t be seen at a baseball game.

It’s the age-old law in baseball: You hit one of our batters, next inning we hit one of yours.

But an attack like the one Thursday goes far beyond any mere sports rivalry. Such abhorrent violence has permanently compromised a man’s life and while it may be natural for fans who genuinely revile all things Dodger blue to want to cause similar pain, further fan attacks will only defame and denigrate the sport that is such a vital cultural institution.

If the World Series championship did nothing else, it enlivened and united fans all over the Bay Area and beyond in unadulterated adulation, realizing lifelong dreams for many while rekindling and creating new loyalties for others. But loyalty to a sports team is not an excuse to send someone to the emergency room, and Giants fans should be wary of sinking to the level of the attackers last week.

Further violence and retaliation in any form – much like the Giants’ 1-3 record – is not the start to a season befitting of defending World Champions. It will be far more rewarding making Los Angeles pay on the diamond during the game than in the parking lot after it.