Movements and communities are not necessarily mutually exclusive, but there are often movements which polarizes or radicalizes. Because we lost our sense of community (due to modernism), movements today generally do not try to build communities.
The split between Lutherans and Catholicism is not a good example of community building. That is an example of exchanges of ideologies and dogma, not really about the exchanges of people and community. A slightly better example might be when my friend brought a group of Thai Theraveda Buddhist monks to visit a colony of Trappist monks outside of Atlanta. They got into the sanctuary and were amazed by the acoustics. The Buddhist monks tried out some chants and then Trappist monks performed some of their own chants. They could do that despite differences in philosophy because there was a sense of ultimately belonging to the greatest whole. It is also not a good example because monks are not ordinary people.
Have you read any of the philosophies about modernism? I think you're conflating religions with the traditional modes. Philosopher Ken Wilbur has some great stuff to say about this. One of the characteristics of traditional, pre-modern communities has to do with this idea of the Great Chain of Being. The name is specific to Western ideas, but the generalization of the "Great Chain of Being" covers a lot of ground, even into Eastern philosophies as well as indigenous, tribal cultures.
It is this knowing that you are part of a greater whole (and that greater whole is part of an even larger greater whole, and that greater whole is a part of a larger greater whole). Religions used to provide that sense of knowing where you belong -- but so did tribal cultures without organized religions. This sense of belonging used to be normative and now it is not. Stable, long-term jobs and unions were imperfect substitutes for what modernism broke. Our hyper-connectedness has exacerbated that separation.
On Facebook, for example, people seek out other like-minded people, not to connect (like you were saying in your homeless example), but more to reinforce psychological ego (the beliefs, narratives, and identities a person develops for a false sense of self). Connection requires opening up, of allowing the social masks to be vulnerable, of mutual impact and sharing. That generally does not happen on Facebook (instagram/snapchat/etc).
> So, you ask whether you can maintain loving kindness in the face of threat/danger/aggression? I'm saying there is no such thing that exists on a daily basis. I don't fear any homeless person unless they approach me in a way that says they mean harm to me personally.
Like you, I generally don't fear the homeless. When I lived in Seattle, there were many that lived out in the neighborhood I lived at, more easily found there than in Phoenix. (You have to hide from the sun in Phoenix).
However, I think you live in a very narrow, and sheltered view. There are places in the world where people do live in fear, on a daily basis. My point is exactly that: threats and aggression to someone's life often brings them much closer to ugly parts of themselves. There are not many people in the world who can actually maintain loving-kindness in face of existential threats. While it is possible, generally, ideals tend to get thrown out the window when the pressure is on and shit hits the fan.
> I think it's important for Americans to see the homeless in our neighborhoods, ESPECIALLY us yuppies, so that we can be reminded of what a shameful failure it is that the richest country in the world still has a homeless problem this bad.
Americans living in rural areas also have it bad, but are not exactly "homeless". One of the cherished ideals is this idea of self-reliance. From their perspectives, all those city folks are crazy. And rural folks would not see themselves as being a part of the richest country in the world. Much of that wealth-building had passed them by too. Seeing laws and government policies that favor disadvantaged groups -- who are largely city-dwellers, must rub 'em the wrong way in a bad way.