Why does it have to be so painful? Why didn't you prevent AIM from installing with Netscape in the first place? What is it that makes the little yellow megaphone guy icon so unnerving? These are the questions that will plague mankind for generations to come.
I can't help you with your angst, but I can tell you how to remove AIM from your Mac. Open up the Extensions Manager. Under Extensions, switch off the item "AIM Menu". Now look under Startup Items and kill both .Launch AIM. and .AIM Promo. (Those "." things are supposed to be bullets.)
Restart, and feel whole again.