There's nothing wrong with respecting cultural differences, but lines should be drawn when the safety of individuals, not just children, is put at risk while on British soil.
And if anyone stands against such action, bluntly put, screw them. If anyone supports forced marriage, or genital mutilation, or whatever else is going on, especially when children are involved, they are part of the problem.
This should not be seen as an anti-muslim problem, or a cultural problem, just a problem of what is right or wrong, and most reasonable Muslims would agree with that.