Liz,
Bob is indeed a nice guy.
Welcome to knife ownership and the simple fact that most people do not understand them.
Because of the lack of understanding, most regard knives as weapons and not the simple tool they actually are.
They see death and destruction, not the "original tool" of mankind.
When the same people see firearms, they see something evil instead of a finely crafted percussion instrument. This unfortunate majority is responsible for statements like "guns kill" or "knives kill" because they cannot fathom that people kill. The tool of killing is not usually relavant to the decision to kill. It follows the decision and can be whatever is handy ( automobile, gun, baseball bat, kitchen knife, drowning, fists, choking grip to the throat or KITCHEN KNIFE)
As a knife owner, you share in the responsibility to teach the masses that knives are tools. This may be done by simply reacting with suprise when statements are made that they are dangerous weapons with "Oh, I guess I never really thought of that aspect", or "surely you don't think this knife will run rampant by itself and injure people".
Pass the issue quickly and never attempt to argue with the ignorant. Their contempt was taught to them by the media and popular press.
On another issue, you said previously that you wore your knife where it is visable to everybody. That's a personal issue to me as I have difficulty associating a "fast draw" clip to a humble tool.
Also, I have more fear of the clip detaching itself and my knife falling away from the safety of my pocket than I have perceived need to instantly deploy a knife.
Be responsible. Be discreet. Teach others well when the opportunity presents itself, and they in turn will likely educate others.
Sorry about your room mate. I'm way too old for you, but I like you. Take care and keep smiling
Bill