It is funny that I come upon this post, because learning to remain positive in the face of other people's rudeness and dysfunctional behaviors can be a challenge for me.
I think it's harder also when you live in a huge metropolis and get to interact with and be exposed to so many different people from different upbringings, walks of life, etc on a daily basis. You really need to develop tools to deal with it all effectively.

Right now I am reading a book called Emotional Intelligence (by Daniel Goleman), and it basically explains how people who are better at dealing with and controlling their own emotions and reactions to others can be much more successful that people with higher IQ's and less patience and people skills. An interesting read, thus far.
It says that developing self awareness, self discipline and empathy go a long way in being able to remain cool in not so comfortable situations and interactions with negative people. I am definitely taking notes! ;)