I actually think the change really happened during the edition wars. I've been on Enworld a very long time, and though we had the fiercest of rules laywers debates in the 3e era, it wasn't until the 4e era that I felt like debate shifted to be "personal". People moved away from logic in debates to more angry rhetoric and attacking the debator rather than the debate. It of course happened during the 3e era as well, but not to the same degree.
Though I feel like that is a reflection of the greater break down in debate I see (at least in America). People really just seem to have lost the art of constructively disagreeing with people.