The thread you reference , is an excellent example of why why one should be allowed to edit and delete posts. The poster in question, I can only guess, deleted his contribution because the tone soon took the form of the typical lula downward spiral - which he presumably didn't care to participate in or else simply decided to recant. Both of which, to my mind, are valid reasons.
At least the thread soon recovered with some cogent contributions, so rather than fuel the flames, perhaps it's a good way to encourage sane participation and avoid the recent, all too common, mod intervention and/or closing of threads.
M