That's a major assertion without much back it up. I have no data either, but anecdotally I'd say you're probably wrong. I grew up in small town america, you don't get exposed to different view points, and if you do the common action is to just deal with the friends you have; there's not much else (this is why the bubbling on social media happens so readily; it's what people are already doing). Also I hesitate to assign people "unfriending" as a negative feedback loop. You get no notification you've been unfriended, and there's no mechanism to indicate why the action took place. If anything it might be reaffirming?
I'd also posit you're underestimating the value of a network of weak connections. This is especially true under the idea that most people will work some place different than where they grew up; reconnecting with friends that drift toward the same hub is a powerful tool.
I'd also posit you're underestimating the value of a network of weak connections. This is especially true under the idea that most people will work some place different than where they grew up; reconnecting with friends that drift toward the same hub is a powerful tool.