comments come through a lot louder than the comments that are supportive. I would agree that the behavior you described definitely takes place. I would also say there are an awful lot of participants on this board (I dare say the great majority) who defend the players or just don't say anything even though they're shaking their head at the more negative comments.
Most of us will make the occasional specific criticism like, "Player 'x' needs to pass the ball back out more more after getting it near the rim," or "Player 'y' needs to stop thinking so much and just let the shots fly when he's open." But for the great majority that's about as bad as it gets.
Those of us in the majority recognize these are kids (even though they're technically adults in some cases) who are playing for love of the game and doing the best they can. And we also recognize that the coaches want to win way more than we do.
Keep that in mind and ignore the harshest critics.