I hate it when criticism becomes personal. I can critisise someone's way of playing, someone's missed goals, someone's faults in defending whatever. Some of the folks here can probably remember how furious I was because a player of Eintracht got the second red card (twice yellow) within a week..
. But in the moment when I hear: "what a piece of shit" only because he didn't convert the chances he had or because he made an error on the pitch, then I get
on the person who says that. The player is no shit, only because he makes a mistake. Go on the pitch yourself and try to do it better, that's my usual thought on it.