We don't know what was going on at practice. I'm sure there was a reason for keeping Tage up. I'm not complaining because of how he has responded once being sent down. Did he deserve to be up? No, not from what I know. These conversations were had all season. Not sure why people would be angry with him performing well.
People aren't angry that he's performing well. They're angry that a player wasn't treated in the fashion that would have afforded him quality ice time, practice repetition, and situational use to grow -- the traditional route of minor league development in the NHL. We see him having some success and wonder at what might have been possible if he'd been working on the problems that plague his game at faster speeds and with less time.
Edit: as for what happened in his time up with Buffalo, this is similar to several posters comments in November when it was obvious that he should have been sent down. We could see his on-ice mistakes with puck security, his positioning, his over-reliance on stickhandling all season. There was no change in what he was doing. Practice implies that he was working on parts of his game that are not working -- which is a broad swath of problems at this point -- and seeing some improvement. There was none. So this consistent party line about him staying up to work in practice at the NHL level holds no water. It did not make a difference and we can infer from how he played that there was no improvement. We also know that practices days for the NHL team are often very limited.
The
only reason that makes sense to see him up all year was that he was a big piece of the O'Reilly trade and that... that points to bigger problems at the top.