No way this is true. No coach is this dumb. I would never in a million years think a coach would call teams to tell them bad things about a player of yours. If he's not coach-able then he'd want him off the team anyway. The high he's picked the better Barnes looks. This sounds like a kid who listens to the "advisers" around him more than the professionals.
This reminds me of a story that Bo Ryan told a clinic, he said that he got a call from an AAU asking how many shots his player would get in his offense,and that he needed to on the staff to make sure his kid was taken care of. The AAU coach said that his player needed to get around 20 shots a game so he could show the NBA what he could do. Bo said final said "my team is funded to get your f**king kid to NBA." He did say who it was but then he went on a rant about Tyreke Evans being born two house down from where he was born and he couldn't get Tyreke to talk with him one on one. Lamont Peterson, Evan's AAU coach, was on staff at Memphis when Evans was their. Lamont even lives with Tyreke right now, and is his "strength coach."
On a side note Lamont isn't the only AAU coach who was hired by Memphis to be an adviser. While schools like Duke, UNC, and Florida wouldn't even talk to these AAU guys Memphis was cutting them checks. The NCAA had to pass rules to stop this. But it was fun looking at Memphis's bench and see 12-15 guys in suits at the end of the bench.
What I would believe is that teams called Barnes and he told them that Hamilton was leaving because he wasn't welcome back. It's like in right to work states when you call a former employer and the only bad thing they are allowed to say is if you wouldn't hire them back.