Why have urban Americans been more tolerant of individual social and cultural differences?

More tolerant then rural Americans? Rural people have had a tradition of mechanical solidarity.. which involves a relatively homogeneous population. People tend to be alike in their beliefs, attitudes, and behaviors. They tend to have similar skills and depend on those around them being like-minded to help hold their social world together [solidarity]. Urban Americans are more heterogeneous. There are many different kinds of people who specialize in some aspect of a substantial division of labor. Urban people don't require others to share their beliefs, attitudes, behaviors, or skills. Instead they depend on the specialists around them to fulfill needed functions that they can't do for themselves. Social solidarity depends on that division of labor and contractual relations [organic solidarity]. Such a system can more easily accommodate a wide variety of different types of people vs. a rural system which needs everyone to think and behave alike. Regards.