Hmmmmmmmmmm......
Well, I don't think it should have been cancelled, that isn't right, but I do think the debate would have been a bit of a stupid affair. Asking someone who has profoundly non-multicultural values whether the experiment has failed or not, is sort of like asking a cow whether it's a good idea to be vegetarian.
It 'might' have been an interesting debate, it 'might' have broken down into a large group of snivelling self-important gits whining about their lot. Either way, to cancel it actually adds media weight to what is, in reality, a very unimportant event.