I've noticed from 1.2 to 1.4, we are slowly given little to no choice but to have multicultural society in the game as we expand our empire..... I think it's bollocks. Bring back purge tolerance for xenophobes, instead of forcing xenophobes to have multicultural society and tolerance for slavery. We should be allowed to purge people without our own people hating.
But the solution to your problem is just purge them. Kill them all.
As of Utopia, Xenophobes will be the only ones who can purge. But some of your people will hate it as not all of your people will be Xenophobes.
If you're not willing to engage in a little bit of violent oppression, don't play the bad guys.