I think this prudish and pompus attitude to new singers is not at all constructive for the movement.

Everyone has situations where they fail, no doubt you have failed in front of people too. And no doubt you know how disheartening it can be.

A supportive environment takes people beyond their failures rather than stifling them. If new people are to come along, then encouraging them rather than telling them not to come until they learn their lines would be a better approach.