I believe that we see our own reflection in other people. The way people react toward you, after they meet you, is actually the way they have been reacted towards since the very beginning or for a very long time. They are kinda used to the reaction and it has become their custom.
So the next time somebody is mean to you, you should know the world has not been very kind to them. Those who are kind to you, are the lucky ones, who are satisfied with their lives and content with whatever nature has offered them. You can actually be kind to the mean ones, as they need to know what kindness is. :-) Who knows, maybe it will change their lives for good.