I think the just the opposite.
Gallo played really badly and D'Antoni knows that if Gallo really focuses, he can usually find a way to play well. Also, anyone could see that AR was too timid as he approached the basket. Instead of enthusiastically going for the dunk, AR was wasting opportunity after opportunity.
D'Antoni simply wants both players to play better, because he wants the Knicks to win. In the longer run, finding a way to motivate both players will increase hopefully increase their value, when the turn the corner, not decrease it. D'Antoni is just coaching imo. The value of Gallo and AR depends on how they are playing in the present. His criticisms will be yesterday's news shortly, particularly if they start playing better.