Actually, I can remember being spit upon when I was a child. I was teased mercilessly throughout grade school. As I recall, I wiped it off and walked away without a word (while the verbal taunts continued).
Regarding the big thing/little thing question in the original post, I don't look for reasons to express moral outrage at any level. Personal affronts are either ignored or met with mild mockery - gotta be careful here cause people get really mad when you joke about their most cherished beliefs. Occasionally a political or social issue will grab my attention but I get over it pretty quickly.
@jimrckhnd's comment pretty much describes my experience. Political gridlock in Washington and financial meltdown on Wall Street don't affect my emotional state as much as stupid computer failures or that DAMN SQUEAKING NOISE that the air conditioner makes. The fucking air conditioner drives me insane.