I assure you I wasn't trying to isolate his problems to motivation. Merely stating that having a stint in the AHL would be motivating.
I can only respond to what you wrote, which was that he should go to the AHL for motivation and perspective, and thus, my response that IMO, motivation is the least of his issues. If down in the AHL would he be motivated to be in the nhl? Of course he would, but that's not why they'd want to send him to the AHL. Your making an assumption (and used an example) that by trying harder and being more motivated can make him better. I'm saying there's nothing to indicate that's the problem or that trying harder is going to help, in fact, in many cases it can hurt as young guys try to do too much and/or grip the stick too tight.
He's a young, inexperienced player who will have ups and downs and will struggle from time to time as he learns how to play defense in the NHL. IMO, "Trying harder", when all indications are that he's already very motivated, isn't going to help.
I'd have no problem if the Canes sent him to the AHL (although I don't think they will) as he needs to learn how to consistently play defense at the professional level. Spending some time in the AHL against lesser (but still very good) competition can allow him to develop his game, play more minutes, and grow confidence without having to worry about the outcome of an NHL game and those are the reasons you send him down.