Love is a Contact Sport
Despite the evolutionary paradoxes of human nature, the perception of who belongs in our group is malleable. H. sapiens as a species has already demonstrated its capacity to expand the concept of group membership into the thousands and millions.
It can be extended further. The best way to diffuse conflict among groups is to diminish the perceived sense of threat through social interaction. If feeling threatened makes us want to protect others in our group, non-threatening contact between groups allows us to expand the definition of who our group is.
White children who went to school with black children in the 1960s were more likely, as they grew up, to support interracial marriage, have black friends, and be willing to welcome black people into their neighborhoods.
Most policies are enacted with the assumption that a change in attitude will lead to a change in behavior, but in the case of intergroup conflict, it is the altered behavior -- in the form of human contact -- that will most likely change minds. The self-domestication hypothesis explains why we as a species evolved to relate to others. Making contact between people of different ideology, culture or race is a universally effective reminder that we all belong to a single group called H. sapiens.