Intent is a huge part of assessing the severity of a crime. If some NRA idiot is shooting at stop signs and accidentally kills someone, he's an asshole and deserves to go to jail, but if someone puts a gun to someone's head and pulls the trigger in cold blood, that is a worse crime, because he *meant* to kill.
Likewise, a drunk driver who kills someone, no matter how reckless they were, didn't mean to kill them. Yes, they deserved jail time, and I actually think a month is much too short. But without the intent, it's in a different category.
So let's be clear about what Michael Vick did. He wasn't just "dogfighting." Vick and his buddies killed dogs that didn't perform by hanging from trees, electrocution with cattle prods, and slamming their bodies to the ground, forcibly drowning them. They admitted to deliberately starving them to make them fight harder.
If you think this is no big deal, next time you see a dog, try to imagine yourself doing those things to him.
That kind of cruel, psycho crap is not a mistake that you express remorse for and move on with your life. You are either the kind of person that does that kind of thing, or you aren't. If Vick was that kind of person, then he still is. And playing in the NFL isn't just "making a living," it's a position of privilege with a huge income and fan adulation. He does not deserve that.
There are plenty of examples in professional sports where people have been allowed to come back who shouldn't have -- Tyson the rapist, for example. But that doesn't make it any more right in Vick's case.