He was suspended because of the charges pending. Just because he served some suspension time, doesn't mean he can't or shouldn't serve more.
So, if a DUI offender, or, Vick repeats the offense, he then should not be reinstated? Why? Why is it ok for them to do something most of us know is wrong (And they know it's wrong too) once, but not twice? Why not three times? The NFL is an employer....And a dang good one. They have the right to deny employment to whomever they choose, just like any other employer.
Right now, if Vick is brought back in, he will hold the distinction as the player that leads the NFL in jail time served. He is the MVF (Most valueable felon) in that sense, so, he is a unique case, that in my mind deserves unique post-prison punishment.