Euphamism,
Interesting points:
I want to add that this is a matter of personality. (If any of you know the Myers-Briggs typology, I think it's often a matter of T vs. F types.) To some people, a person and their ideas are separable. They will happily attack a person's ideas, and don't understand why the person was hurt or offended; they were merely attacking the ideas, not the person. Conversely, they are happy to have their own ideas attacked, and don't mind defending them.
I'm an INTJ. I wonder if that has anything to do with it?
Of course, as an INTJ I'm even skeptical that Myers Briggs typologies are nothing more than bunk, but the INTJ typology does seem to fit me to a T. hehe
rem