Well, considering she said they can't act or sing, that was she was #horrified, why shouldn't they? It was bitchy. It was not constructive.
People need to mind their words more carefully now.
There's the 'ol three block rule when you've seen a play- wait three blocks before you start yapping because you don't know who's around you.
There should be a "don't badmouth performers and productions on Twitter" rule.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."