Yes, that's because kids don't know how to judge others, they simply don't have the experience.
That's true, but isn't it admirable, what they do and how they act? When you bring to a child's attention that there's another child in the room, or in the other car their lips curl into that unmistakable cute, and happy smile then giggle, cocking their head to the side in a manner that only a child can pull off (and still look cute) and repeat what you just said, that there was another kid. Some might even go so far as to wave and call to the child-it's just so cute and it's something we, as adults should be able to do.
I know, some kids utterly detest the fact that there is another child someplace near and that they would rather be the center of attention however the kid won't hate the other. It never gets to 'hate' not even dislike. Maybe discomfort, but that's all.
Now I'm not saying start waving and laughing like a moron when you see someone else, but shouldn't we try to be as willing to smile and not judge others like kids do? Give people a chance, because when you do give people some slack and not judge them, they'll do the same. Being positive/tolerant is contageous.
They say that the older you get, the more you learn but what if what we're learning to do is just be inconsiderate and cold? There's a lot we can learn from children, and the best we can learn from them is that by nature, we're actually caring beings regardless of what genre of music we listen to, what clothes we wear, or what we believe in.
People are good, and we should never disbelieve that. Great civilizations were built by trust and tolerance (Roman Empire, McDonalds, Ottoman Empire) and they two of those fell when trust was lost and people began to dislike others based on even the smallest facts.
Our civilization today is begining to crumble, what with the politics and such. I think we should all learn to at least get along.