Agree, the Mariners games are attended by polite fans. So far. But now that the "12th man" (institutionalized rude noisy fan effort) has become popularized by the mayor and the media and even credited with helping win the Seahawk's game, I wouldn't be surprised to see Mariners fans jump on the bandwagon.
But when the Raiders moved to town in the early 80s they attracted an altogether different element. Major fights in the stands at nearly every game (one Steeler fan was knocked into a coma) -- not exactly a family-friendly atmosphere.