Differences in Thoughts

I'm in a pondering mood this morning and started thinking about differences in people. What makes us unique? And why can't we accept uniqueness and let bygones be bygones? I say this but I'm not good at this. I had a talk with a friend about being a vegetarian. I could understand the concept. But I couldn't wrap my head around a tofurkey and couldn't help but think his idea about not wanting to waste resources so walking in the snow for a mile is still a viable option. And I think to myself that it makes sense in so many ways and yet I still don't understand any of it. The most bizarre thing for me is the fact that it matters. It causes separation between us.
So I wonder, why do we search for differences and similarities with people? People are all different. Depending on how hard we look we will find something different. They can be little things--and I've seen discrimination upon it. And often it goes both ways.
Peoples opinions on love differ. I've seen an argument between friends on whether or not you can fall in love quickly. When in reality it goes both ways. Some people need time to fall in love. The experiences they've had or their personality allows for them to need time. Others fall suddenly and easily.
People differ on ideas and philosophies. And I'll admit I see some as wrong--mostly because they are different to me. But I'm coming to realize that if they make that person feel genuine then there's nothing I can do. I may have my differing opinions. I am just as biased as any person.
That's not the point of this post. This was just on my mind. And I wonder why. I know that I feel validated when I meet somebody who has similar ideals. But why do I feel threatened by people who are different? It's not a bad thing to walk to work everyday to preserve our natural resources. And yet I still note these differences and sometimes slander them.
And I wonder why it matters. Why do I care so much about silly differences? Why does it matter what color someone is? What religion they practice? What clothes they wear? How they fall in love? Or how they get to work?