Acouple of points as I see them:

In this written forum it is easier to be nasty to an 'opponent' than it would be face to face. I've seen some published letters from erudite and learned men (usually men) that are agressive and abusive, and would likely get the speaker a bloody nose if they were spoken rather than written.
There are visual clues to the mood of the opponent which are missing in correspondence, and these clues give the protagonists time to retract or explain. After you have clicked the 'submit' gadget it is too late, and you have no chance to say 'Look, lets have a drink and I'll explain.." so you go to bed and think "The bastard! I'll have to..."

As for going for the weak points, Hell yes! Why attack the strong ones?