In these kinds of situations, people like to say things like, 'He made a mistake' and 'Everybody makes mistakes.' Well, I think we need to distinguish between different classes of mistakes. Some mistakes display a lack of judgment - some sort immaturity or lack of emotional control or intellectual prowess or something along those lines. And then, some mistakes necessarily tell us something about the nature of a person. There are some 'mistakes' that you can't make unless there is a fundamentally evil part of you - there are some mistakes that can't be explained by momentary lapses in judgment, they require a certain evil quality.
For instance, getting drunk in a bar and making an inappropriate sexual comment to a woman might just be a mistake - a failure of judgment, a show of bad form, a display of #######-ishness. But, raping a woman can't just be a mistake - it requires an evilness. It's not something that most people would be capable of doing, even if their judgment failed them. In order to be capable of doing that to someone, you have to be fundamentally evil inside.
Well, what Vick apparently did to those animals was evil. It wasn't just a mistake or a lapse in judgment. It required a certain degree of evilness. And that is something that is either there or it isn't. Typically, it doesn't go away - you just learn to control it because you realize that society has a different set of rules about what is appropriate; and, to the extent that your own instincts run contrary to those rules, you have to control them so that you don't face negative consequences for them. I don't care what anybody says, Vick's actions prove that he is evil - he may never commit those kinds of crimes again, but he has a nature which would allow him to - and most of us don't have the nature required to be able to make that kind of 'mistake'.
Please note, I'm not equating what Vick did to rape - except in the sense that each of those crimes requires certain natures, on the part of the offender, that aren't present in most humans.
On a less serious note, I really thought Cleveland would sign him - can you imagine the marketing opportunities?