In the military, forced integration at work is required. 

The Officers and Senior NCOs are the enforcers.

That is the way the civilians have set it up to meet their social goals.

Off duty, everyone has choices as to with whom or how they associate.

Interests that cross races do exist; car guys with other car guys; pool sharks with other pool sharks, whatever.   

Fishermen and hunters are the same.  The Rod and Bottle Clubs are usually fairly integrated.  All those lying fishermen need other fishermen to  lie to about the one that got away!