While in NY, Vigneault called him out as immature and it's well known he got into a spat with Henrik freakin' Lundqvist.
Lots of rumours the TB room thought he was immature too.
Then he gets into a well known feud with another player in VAN, has public outbursts on the ice and bench regularly, and gets into a well known spat with the coaching staff - which prompts the team to force him to go on a "leave of absence" to cool off. When they realize the behaviour will never change, they are forced to trade him.
He has former teammates publicly saying he is way too abrasive and rubs guys the wrong way.
This isn't making anything up. All are well known.
This is who he is. NY traded for him because a new GM almost a decade later has a weird hard-on for JT.