1) Violence is SUPPOSED to be a part of the first two, not the latter. Hence, in the first two, players are protected from "non-sanctioned" violence. In fact, if you want to end NHL fights quickly, ban ANYONE who takes off a helmet or gloves. Otherwise, let 'em at it. They can't hurt each other.
2) "Gang" behavior is seen not at all in the NHL (for obvious reasons) and to a far lesser degree in the NFL. Teams like the Cowboys, Redskins, Colts, Chiefs, Chargers all retain quite traditional uniforms, especially with the tendency for "throwback" uniforms. Basketball, on the other hand, is emulating the gang styles as much as possible. Moreover, the scanty nature of the NBA uniforms encourages people to sport tatoos and weird hair styles. Aside from McQuarters, you see very few oddball hair jobs in the NFL---and even if they have them, they can't show them.
3) Far more than the NFL (and forget the NHL in this regard) pro basketball has built its marketing around the "don't dis me/in yo' face" hip-hop gansta appeal. I play a lot of the Playstation/X-box games, and they ALL feature this type of music and culture.
The zone helps with some of this, but eventually only very strict foul calling will restore the pro game to one of motion and passing, not back-downs and dunks.
At the pro level, you have to have a higher IQ to play. What's going on, on the field is so complex the stupid but gifted get weeded out quickly.