humans are only animals trying to survive. we are therefore selfish. greed ("want") leads to sadness, jealousy, anger, and all negative human emotions. it's a buddhist principle that you free yourself of want to attain self-actualization (which is nearly impossible from what i understand).
what seperates us from other animals i think is our ability to 1.) empathize and 2.) be self-aware. but just because we have these abilities does not mean that all people hone them into effective practices.
why do some choose to recognize these behaviors and others don't? who knows. chemical makeup, i.q., abusive childhood, the receptiveness to our individual ids, nature v. nurture, an infinite number of variables.
i always say empathy and self-awareness are next to godliness. truly empathetic people never consider themselves better or worse than anyone else because they recognize the randomness of biology and environment (chaos theory, on and on); that it's not necessarily someone's fault for being the way they are.
that having been said, i don't think anyone appreciates being treated like shit, regardless of their levels of understanding or empathy.
people attack others for whatever choices they've made or some other issue du-jour because they are insecure about their own beliefs on the subject. it's the way that homophobics are probably homosexuals -- methinks thou doth protest too much...
those who raise their voice or yell while trying to convince you of something do so because the facts that back them up are faulty or non-existent, and they know it. there's some cliche that says you can always tell who loses an argument by the first person to call the other a name -- they can't validly attack the message so they attack the messenger.
intelligent discourse is healthy and frankly a necessity in civilization, but it rarely happens. it's been turned into shouting matches on television between selfish people trying to advance their own careers instead of any idea. not respecting another point of view, or choice, and being an asshole is a sign of weakness and insecurity. i just watched "revenge of the sith" this afternoon (not that i'm a star wars fan AT ALL, but i had it at work, no boss... what would you do) and it occurred to me that, as powerful and gifted as the darth vader guy/kid was in regards to the force and all of that sci-fi whoosifuzz, he showed great immaturity in controlling his own emotions. he had not the ability (easy now, yoda) to recognize the greater good and submitted to his own greed. what good is any talent or resource if you don't have the sensibility to operate within a utilitarian society of equals? it's intellectual fallibility.
"good" and "evil" are relative terms but their meanings differentiate them in the vast majority of instances. for example, we can all agree that murder and stealing are more evil than good, but occasionally you get the robin hoods or new orleans victims stealing food for their children, but the instances are rare.
my treatment for dealing with the assholes of the world: don't let them bother you, or rather try not to let them bother you. i know, always easier said than done. it's hard to control what other people say or do. it's much easier to just control and condition our own reactions to what others say or do.