People need to remember that Manziel is still just a kid. How mature were most of you when you were his age? How mature do you think you'd act if you were a 19 year old Heisman trophy winner with all kinds of ... attention ... being thrown at you all of the sudden.
I'm not saying he'll ever grow out of it. He could end up staying the way he is permanently. I can't speak for you but I know I wasn't the most mature guy on the planet at 20 years of age. And I didn't have the kind of attention thrown at me that he has.
That said, no way would I want him as a Cowboys QB, but that's mainly cuz I don't like this "College" brand of football that now exists in the NFL. I like my NFL QB's to be passers, not gimmicky read option garbage. If this continues, and isn't just a fad, I may have to find something more entertaining to do on sundays. It's already bad enough that the "Enforcer" position in the secondary is a thing of the past. Now the pure pocket passer is in jeopardy too?