I don't feel that constructive criticism's a totally bad thing.

In many sinarounds/informal do's, the audience seem obliged to applaud at the end of a performance, irregardless of the quality.

Therefore, most performers have no way of judging wether their efforts were good or not.

I [& others] have been known to offer positive, helpful comments to others, if I/we felt their wasn't as good as it might've been.

Merely saying something like 'That was crap!' does nothing useful for anyone & just creates resentment & bad feelings.