Let's not kid ourselves that our society doesn't harbour an awful lot of atavistic inter communal hatreds just beneath the surface, not likely to break surface in conditions of reasonable social peace ... BUT get an economic collapse on the scale of the Great Depression and all bets are off - communal tensions could well take on very alarming forms. I'm not for a moment suggesting this is imminant - but we all have to remain vigilant. Remember that in the catastrophe in Yugoslavia some of the worst mass murderers had previously led blameless lives as things like icecream sellers or sports coaches.
As I pointed out above, though, Yugoslavia shows us that its possible to have ethnic bloodshed on a mass scale without anything resembling fascism gaining control of society. Despite all that went on, and despite the resulting rise of some politically dubious bastards, the territories of the former Yugoslavia resemble a society just like this one-just as it did, despite one-party rule, before it descended into madness.