As weelittledrummer said "The work we do does not exist in a vacuum and and it gains at least some of its validity from the audience." If the effect of the production has been to ensure that it won't be seen by Sikhs, that is a loss which I am sure would not have been in the author's mind. You can't challenge people to look critically at themselves if you have driven them away.

You are in grave danger of falling off of the fence.

Again you seem to be blaming the production for the fact that the play has been prevented (by a mob). It is hardly the author or production that have driven this audience away. Unless it is because they did not agree with the protesters requests or the alternative (gun to the head threat) - if these requests were not met.

The right to protest about a view, that a piece of drama may express and to leaflet the audience, is one option - but not the only one. As you have said this protest (and its lawless result) is an option that will bring attention to something that many folk would never have been aware of.