Typhoon All different categories of stupid.
Achlicter was an addict to gambling.
Leaf was just immature and angry and exposed under pressure.
Vick was just an enabler of behavior he honestly saw nothing wrong with. If the public had never heard about that then it's no big deal in that community.
Manziel is an addict as well, but as he's already demonstrated he's in denial. You can force a denier to rehab, but he won't change. He's far too immature and stupid to change IMHO. Any team that gives him a second chance ought to do so under a contract so incentive laden as to make any future stupid move by Manziel a cutworthy expense. As an example, you basically pay him per play, per start, per game. You give him an NFL minimum contract with so many incentives as to basically force him to either produce or you've lost nothing. The tell will be if Manziel is willing to sign something like that. If I am a QB desperate team, you bring him in and offer him that. If he balks at it, you have your answer.
Trying to think of teams that might consider him, and I've got Denver (unlikely beyond the humor of it), San Francisco, LA Rams (it's still wierd to say that), Chicago and maybe the Jets, depending on how their deal with Fitzpatrick goes.
There are a few other teams who might consider him as a potential backup under the same type of contract, but if you offer him a backup position with an NFL minimum and incentives he's probably not going to go for that. But Detroit, Arizona, San Diego, Oakland, Kansas City, Indianapolis, Dallas or Philly might throw him a bone just to test the temperature.
I mean, at this point, if this kid ain't humbled, there isn't any team that would be stupid enough to sign him. OK, I forget that Jerry Jones still exists (and Daniel Snyder for that matter), so pardon me while I retract that with an *.