A group of middle-class white guys will bond more quickly and easily than a group that mixes white guys and low-income black women.
So where do you draw the line? It's clearly not OK, even in the name of "cohesion", to encourage a culture that excludes people of different income levels or ethnicities.
Because that's not how human beings bond. We don't bond over a single facet of our lives; we bond as a community. The modern world, in which we live different places, believe different things and pursue different jobs, is poison for any sense of community.