I dont think calling someone a "jew" is patently offensive, although it does sound a bit abrasive. Just say jewish if you're concerned.

I consider an idiot someone who is a) not only stupid but b) does something stupid. I consider a doofus someone who is dumb, but doesn't know any better. The difference being, two people going to the will call at a concert. The idiot having done will-call several times and knows the procedure doesnt bring his ID. He is an idiot. The doofus just has no idea what he has to do. weak example, but i'm in class right now... cant think much.