Feeling is such a weird thing

How do we have feeling for things and people? Why do we have different feeling towards different people? Is it because of the appearance that causes us to have such a vast different towards all things in the world?

I used to judge people by their look when I was young, and I realized that we all really need to judge people by their heart, and their thinking. But as I grow older, I start to understand the important of such stuff, as in we people do think differently and we have to accept everyones' idea. Just like in science, a thing or idea is never wrong unless you prove that it is. So we can't judge a person or an idea unless we know that the person or idea is wrong too.

But I'm really curious that why do I have such a different feeling towards different people, I understand that I'm being unfair and is wrong to do so. But I still react in this particular manner, is it because of I do not believe in that idea of mine, that's why I am reacting this way.