The fear of the unknown leads to a propensity of violence. In Latin the word "hostis" means not only enemy but also stranger. So, if one is able to convert a stranger into a familiar person, the enemy might not become a friend but at least an ally.
In socially problematic areas, you often find opposing groups which do not know a lot about each other. The ignorance of the other leads to a de-indiviualization and to a down-grading of the opposite group (outgroup-effect). This leads to a propensity of violence towards the other group. The challange is now to bring the opposing groups to perceive the heterogenity of the other group and to see a group of individuals rather than a homogenous group of non-individuals.
Global Emotion has developed an online-training capable of breaking open hardend group borders. Interested?