Similar to what happened with Nicole Holder, none of us know truly what happened behind the scenes with Greg Hardy in Dallas. People can guess and speculate, but no one really knows.
There has been some things that have leaked out indicating that, at the very least, Hardy wasn't as punctual as he needed to be, especially on a show-me type of contract. At worst, apparently, Hardy called out the head coach of the team in front of the players, and called him a derogatory name.
Now, I will say with full candor, I have no idea what is true and what isn't. Obviously, versions of what took place are put out there by people with agendas of some kind - those who don't like him, those who may be competing for a roster spot with him, those who perhaps endured this aspect of Greg Hardy's alleged personality and behavior.
I will also say with full candor that I wasn't in favor of signing him last season, and have not wavered from that point of view.
That being said, if, as has been alleged, if he had a tardiness problem, that can be managed. It's an irritant, and can disrupt the flow of meetings, practices and the like, but it can be managed. If this is the extent of the problem that Greg Hardy presented, it does show a lack of self awareness on his part, knowing that eyes are on him and he still can't manage his time properly when he's on a one year contract. But, that should not be a disqualifier for him being brought back. Again, it's a management problem.
However, if he indeed called Garrett out, and called him an expletive in front of the team, that's a whole other ball of wax. There are lines that simply cannot be crossed without consequences. I don't care how raw locker rooms are, you don't call your coach the B word in front of everyone, and not have to be held accountable for it.
Where I wonder about whether this took place is that Hardy's playing time was never reduced during the season, and he was never suspended by the team. It would be odd for this to take place without something being done. Hell, it was reported that Marion Barber was fined for violating the dress code on a flight - think that this may have warranted the team announcing something?
And, if it did, and Garrett did nothing, which I can't see happening, then he has no control of the locker room. If he wanted to, and Jones blocked him from doing it, then he has emasculated Garrett in a worse manner than he has any coach that preceded him.
Whether you like Jason Garrett or not, that would be the absolute worst outcome possible, because it then means that no coach would have a chance here as long as Jerry Jones is alive, and running things.