Good, more teams should do this.
He is just being selfish and extremely immature right now. And you know what? That's okay! Young people go through phases like this, so it's not like he won't grow out of it, and the hope that he does. But whether you're a professional basketball player, or working in an office, you go through things like this as a young person, and you learn to be professional regardless of your grievances. 
This is why drafting young players is such a tricky thing, because on paper, they could have all the skill in the world, but if their mental make up isn't there, they may simply not get to their full potential. I see snippets of Wemby's interviews, and man, for his age, he is just so grounded and well spoken, you just know that he was raised well and has a good head on his shoulder. The same with a lot of the players on our roster as well. 
That all said, it doesn't mean that Ja won't put it together, he is just clearly going through some growing pains, I know I was still growing in to being an adult at his age myself, and I only really began to settle in my late 20's.