Fallingsout With Friends

I'm angry at a lot of former friends--
Why does this seem to happen as one grows older?

One couple: boring
A woman: right-winger, attacked my left-wing views
A lower-class woman, defended Sarah Palin
Old friend, male, verbally abused me in front of friends
Woman I admire--rarely contacts me
High school friend: bullied me
Another high school friend: ignorant, shallow political views (anti-Obama)
Still other high school friends: snooty, rude
Neighbor: desperate to show how knowledgeable he is--rude--arrogant--