Why dont multicultural societys work?

Zimbabwe and South Africa are perfect examples of one side having power and then losing it and in the end what happened to the former is bound to happen to the second one. Maybe its more of a power struggle and first against third world but these arguments hold true for asians and afrians coming to Europe apart from a few exchange students who have the intellect to see that to get on they need to dump their third world baggage and integrate. But the over whelming majority seek to create their own ghettoes and its only now some of the excuses for politicians are waking up to a problem that is growing 20 heads that is a waste of resources. Before m immigration racisim wasnt even a word in the dictionary now we need to cater for these peoples excuse making because they are clearly not capabale of being integrated and will forever be a drag on westerners having to make excuses for them. The best solution is m repatriation.