Seems to me we are all components of the whole... Including all sets of opposites, balancing out each other, perhaps striving for harmony. We may all define ourselves in one way, separate of our opposite counterparts, but we are all fractional making up the whole.
We will Create Division and Fractions!!!!
If we truly were one, and could feel the pain and joy of others etc., then it would make sense that people would be nicer and more helpful towards each other. That's not the case though. I mean we can be compassionate and empathetic, but it's not direct. Is that because at some point we all grew apart from each other? Would that even be a valid theory on it? As far back as people go there was harm done to each other.
I think it's just a matter of perception. We can only perceive our little piece of the universe and only experience our own bodies directly, and this makes us feel like self-motivated individual units. It takes a different kind of perception to realize oneness, and it is not tied to religion.
Unlike the guy below me, I like the article. I fear that tribalism is a stronger human drive than a belief in oneness, nevertheless.