There's a BIG difference between what Stallworth did and what Vick did. Yeah, Stallworth killed someone, Did he go out and say I'm gonna go kill me someone??? NO. What he did was incredibly stupid and selfish in getting behind the wheel drunk, but there was no intention of killing someone. Stupidity let it happen. If he pointed his car at someone and knowingly mowed them down, I'd want him behind bars for good.
Vick however had every intention of doing what he did and what he did was beyond cruel, it was evil. H'e didn't just bankroll the operation, he shot, electrocuted, hung, drowned and slammed repeatedly to the ground underperforming dogs, not to mention the dogfighting itself, where they press the dogs to rip eachother to shreds. I'm so da mn sick of people saying "they're 'just' dogs". So that makes this horrendous treatment ok or less vile than if it was done to a human? I don't think so! They feel pain just as much as we do and have NO choice in what they are made to do or made to suffer.
The difference is that Vick intended to inflict incredible pain and suffering on these animals and he ENJOYED it. That wasn't Stallworth's intention at all.