To begin with "State Multiculturalism" is not the same as "Multicultural Society" and we need to look at what David Cameron actually said rather than the media headline.
He has stated that there should be greater scrutiny of groups the receive public money but do little or nothing to tackle radicalism and extremism within their groups and the wider community. I agree, he also stated that Ministers should refuse to engage with such groups and they should be denied public funds and the opportunity to spread their message in State institutions such as Schools, Universities and Prisons. Again, I agree.
He had called for the State and Society at large to judge these organisations, and do they embody those things that the UK hold dear, such as Universal Human Rights, Equality in Law, Democracy, and do they encourage integration in that society or promote separatism. I have argued on various occasions that separatism is the biggest barrier to a true multicultural society where all peoples regardless of faith, colour, culture live together and share and learn and revel in each others differences rather than what currently happens and we shun each other, that is not a multicultural society, that is a collection of mono-cultures separate and suspicious of each other.
Importantly, and this is something many people who post in these forums do not seem to grasp Cameron said "We need to be clear. Islamist extremism and Islam are NOT the same thing".
I agree with him, we do need a National Identity, one that promotes our ideals of Freedom of Speech, Freedom of Worship, Democracy, The rule of Law and equal rights regardless of sex, race, orientation or creed. These things are what define us and if you wish to be a part of this then you are welcome, this is what is means to belong to the British Society and this is what you must embrace.
To be a true multicultural society we need to be united, and we need to united behind those values which define us as a Nation and as a People, and it matters not whether you are Black, White, Jew, Muslim, Christian or otherwise....We are one Nation, we believe in Liberty, Democracy, Equality and Tolerance and if you do not agree then Britain is not the place for you.
That includes everyone, not only the Muslim extremists, but all the racist, bigoted groups such as the BNP that rail against them so much also.