*snrk* I know the feeling. Dunno, maybe it's because you make good points, and the people who agree think there's nothing left to say and the people who don't agree can't think of a way to argue?
Had a conversation along similar lines the other day, and think it's my personal opinion that there's two main kinds of fanfic - 'serious' and 'playing around.' Admittedly the lines can blur sometimes, but there's really a basic difference in approach between whether you're trying for a canon-consistent base or you're just playing with some of the ideas and doing what-ifs. This is wny a lot of us prefer there to be AU warnings on the latter.