Livingstone has responded by claiming it is JS Mill's famous 'harm principle', rather than Marxism, that forms the basis of his support for multiculturalism:
"Multiculturalism has nothing to do with an assertion that there are no universal values. The very statement that people should only be able to do such things that do not interfere with others is clearly an assertion of a universal value. In so far as they do not interfere with others, people should be able to chose freely which values they wish to pursue. A person, for example, may wish to wear a yarmulke, a turban or a hijab or none; they are free to chose."Hardly a clash amongst intellectual titans, is it? Whatever else Livingstone might be, he certainly isn't a Marxist, so Cameron's wrong there. And I'd also agree with Livingstone's liberal defence of people's right to wear what they choose and follow the religion of their choice and so on. Beyond that, there's a couple of problems with his use of Mill.
Mill was concerned with individual rights; multi-culturalism with group rights. These two goals can obviously clash if the latter are ever internally intolerant of the former.
Like some on the left, Livingstone fails to distinguish the personal from the political - perhaps because he doesn't believe in such a distinction, I wouldn't know. With his harm principle, Mill was concerned with defending an individual's right to make choices free from interference by the state. But he did not do so on the basis that we should therefore approve of the choices people make - only that state interference was a greater 'mischief' than that which people can do to themselves through 'self-regarding actions'. This doesn't really have much to do with the celebration of diversity that I assume Livingstone is envisaging when he invokes JS Mill in the way that he does.
With these two considerations taken into account, along with the fact that Mill was a strong supporter of women's rights, while Livingstone is probably correct to suggest that he would have defended, for example, the right to wear a hijab, it seems unlikely that he would have seen it as an expression of multiculturalism to be celebrated in the way that Ken Livingstone does. Anyway, while I share Livingstone's aversion to anything that sounds like a compulsory state monoculture, I don't think Cameron, and before him Trevor Phillips and Jack Straw, were actually suggesting there should be one. Moreover, even if they were, Mill would have, of course, defended their right to say so.