Bob, I'll join the chorus. Welcome to the world's greatest hobby. I suspect the proportion of jerks among ham radio operators is about the same as in the general population. They just have access to microphones and keys and...as you have noticed...the Internet.
If you join Yahoo groups or visit chat rooms devoted to other hobbies or pursuits, I think you'll see the same few blow-hards who give those avocations a bad name and probably scare interested folks away. And I honestly think we are more aware of on-air amateur radio crackpots because they stand out so much from a mostly civilized bunch of good guys and gals. Dial away, ignore them, don't respond to them, and they'll lose the one thing they crave the most and will do anything to get...attention.
73 and good luck on the exam. See you on the air soon.