It takes time. I am a firm believer of system instead of people. That's why I believe, and history supports my view, that people are similar despite all the differences in race and culture. Once the relatively right and safe system is in place, people will be more adaptive and tolerant, for their own good.
Ethnic tension or religious conflict will always be there, but without a dictatorship, those conflicts cannot be abused to force the whole nation en masse to a war.