It's the basic arguement of first impression.... Once we've made our minds up it's difficult to change them and the longer we feel a certain way the more difficult it becomes to change that... I believe it's more of a side effect the way our brain is programmed... The basic concept that the snake will only get a chance to bite me once cause after that i know he'll try agian.... Like zebras at a water hole..... They remmber that there are crocodiles and they are leary to take a drink because the first time they saw a crocodile was probably in the watering hole..... Its a defense mechanisms, biasness, Keeps from making mistakes.... Well at least it's suppose to...

Yeah it's true that every human have biased thoughts on things that matter to them, but the goos people in the world keep their minds open and are accepting of other peoples opinions, then maybe the bias will shift just a little.