I can't say I really blame the kid for the tweets. He was upset and from what I can tell... He has every right to be.
When you are an athlete being recruited to play college ball, you are making a decision about your future just like kids who aren't being recruited to play sports. The difference is that when you select a school, you are putting your trust in the hands of the coaches recruiting you and they have the power to really mess up your future.
I was in a similar situation as this kid. I was recruited by a couple of different schools to play soccer. I chose the school I did, because the head coach of the school that recruited me was the first coach to start recruiting me and he made me some promises... and he ended up keeping none of them. I ended up not playing there and after turning down those other schools and having a year pass where you are stuck at a school you don't want to be if you aren't playing your sport... You don't have those same opportunities and it is upsetting. I ended up not playing soccer anymore.
Just like me, this kid had other options, but he trusted the coach and the coach didn't stay true to his word. Coaches obviously watch recruits play before the pursue them... so for this coach to act like he was surprised about this kids strength/conditioning is ridiculous. He knew what he was getting.
To me it sounds like the coach is lying to his recruits and it is a shame, because there is really nothing the kids can do about it.
He probably shouldn't have tweeted such things for the sake of keeping other schools interested, because it definitely didn't do anything to help his situation, but he is human and when we get upset we make irrational decisions sometimes.
I feel bad for the kid and his mom. That is an unfortunate situation. Hopefully he can get back on track somewhere else.