It can be "a" factor, but does that mean any play that causes an injury nets a suspension? No, that certainly hasn't been the case. Was Wade suspended for pulling Rondo down? It caused an injury but the league said there wasn't intent. Tons of players get hurt to varying degrees with no suspensions.
And to square that with Smith getting two games for an equally injurious fist, and him having a history of that kind of action, just doesn't make sense.
If that is how the NBA works, Chicago should have someone punch Lebron. Maybe he gets hurt, maybe not. At worst it is a two game suspension.
Intent has to be the bigger part of all punishments, not just in the NBA but everywhere. Intent to be reckless as well as intent to injure. Arm fighting goes on every single play in the NBA. I don't think anyone could reasonably conclude that tugging on Love's arm during a scrum from the ball would lead to a separated shoulder, especially when Love initiated the contact. Throwing a punch with a fist, or using both hands to shove a player in the head and/or neck are actions you could reasonably assume will lead to injuries whether they do or don't.
Ron Artest throws an elbow, its 7 games. Smith throws a fist and its 2? Explain that?