Agree with Aloha, as usual.
Except that I do feel strongly that the authorities/the public should not be prevented from criticising things that, in this country, we see as wrong or illegal, even if the people who carry them out claim they are 'cultural' or 'religious' practices.
I'm thinking of, e.g. female circumcision - until very recently there's been very little attempt to protect girls from immigrant communities who are subject to this, although it is unlawful here. There's been very little activity on the part of police or social services to prevent girls being sent out of the country to be assaulted. Or to educate immigrant communities into understanding that it is illegal.
And the play Bheti (not sure of spelling) that was cancelled in Birmingham due to violent and threatening mobs of young Sikh men. This was a play criticising the treatment of women - yet the police allowed violent disorder (a crime) and threats of violence (another crime) to force its closure. And a woman Home Office minister connived at that decision and refused to condemn the mob or take action to ensure the play could be performed and people who wanted to see it could do so. Seems sexism, or hatred of women, is seen by some people as OK when it's practised by people who use cultural excuses.
As for nativity plays, I do think it's important that immigrants to any country are encouraged to understand the culture of that country - particularly schoolchildren growing up in that country. Our history for the last 1500 years has been dominated by Christianity. You can't really understand our laws, our history, our art, literature and culture, without some basic understanding of Christianity. Doesn't mean you have to become a Christian, or be taught that Christianity is the one true religion. But you should be encouraged to learn something about it because although things are changing, it has been the dominant force in the development of this country and Europe (and North and South America and Australasia).