Dorayakii:
You put forth a very interesting point. I felt and still feel at times (though rarely) the same as you describe, wanting to fend off an affront to my personal belief when someone challenges me. Although I have learned an effective way to deal with that and approach ideas more clearly, I had never thought about the reasons why someone, me, may feel that way until you presented the issue here.
I imagine that it's a natural tendency to feel protective and defensive when some part of our core belief is challenged. That very admission to myself makes me ease-off when I'm challenged and makes me question my own position. Then there are the teachings with which we have been inured. There's a reason why JWs and other cults repeat the same shit over and over again. Somehow, it bypasses the logical centers and becomes autonomic. I recall having a gut reaction and a curt reply when I was still a Witness and someone at the door would say something bad about Charles T. Russell (obviously they knew more about him than I did at the time). I remember being aware of the moment and being slightly surprised at my reaction. I suppose that such behavior is also a natural consequence of being a JW or any group that uses the same tactics.
I also think that a person's experience, how he or she was shaped mentally and not necessarily by a cult, determines their inclination to react poorly at being intellectually spanked. I face that constantly with good friends that I ride motorcycles with but can't carry on a dialog over E-mail on subjects like religion or politics without being totally polarized. Like you, I've learned to keep quite when needed long enough to determine if what was said is even worth a response. If it is, most of the time it's because the person challenged me sufficiently to evoke ideas that are worth exchanging. Other times, it's because that person needs to be either more informed or dressed down. I only take the gloves off with my friends, though.
After being so certain about what the future would hold when I was a JW and after being so devastatingly deceived, I've come to be in a place where I can sincerely doubt everything. I feel very much like Descartes: I know I exists ("Cogito ergo sum"), but I'm not too sure about you or anyone else. I believe you exist along with the rest of the world as I perceive it, but I can't prove it. That premise makes me less assailable and more accepting. Old habits die hard, they say. So, I may slip up once in a while.
Etude.