Right, I get that.
We don't know how those teammates actually stack up against him, though.
There just isn't enough information to say "the coach is justified" or "the coach is a putz."
From what we do know, either of the following scenarios are possible:
Justified: There were other players who could do a better job than Burruto, on the balance. If he had made the team, then another, more-qualified player would've been cut.
Putz: The coach saw the prosthetics and decided "no way is this gonna work," regardless of Burruto's actual skills (or many variations thereof).
From the video and from Burruto's account of his playing career so far, I think it's quite possible that he had enough skills to legitimately make the team. Not to be the best player, or to get a baseball scholarship, or to become a pro. Just to play on the high school team (which I think has intrinsic value, not just a waystation).
I'm not saying that IS the case, but that we don't seem to have enough info to say it's NOT the case, either.