I am suprised that nobody has yet looked at the constitution and approached the Charity Commission. This needs to be done by a local Sikh.
The protest etc is a short term solution, longer term is as above. We live in a liberal democracy, where there is freedom of speech, the right to a private life (function) etc. However there are also Laws in place, to ensure that these rights do not enfringe on other rights and freedoms and also have an negative impact on society.