Unlike today they picked on a select few minorities to create the hate and fuel the conflict. Today you have a similar system in the channel of propaganda and control. Now that people have been displaced from their native land either by economic pressures, war or promises of western wealth the Evil game can begin. Instead of attacking minorities they will over promote them. The end result will be the same when the backlash comes but your leaders blooded hands will look clean.
People form allsorts of bonds from race, religion, work, sport, interests, etc.
These are personal things and the vast Majority of people accept the differences living side by side doing their thing and mixing by their own choice with who they like. People should be treated equally under the law - apart from being human that is where the equality ends. An attack or persistent abuse can only be dealt with as that. As soon as you start to look for minority reasons the trouble starts. Fortunately the vast Majority are good and the only things that should be concentrated on are the things that are important to them as people.