The previous ones didn't.
I have to say I think anyone who takes even a brief glance at that thread is going to see what Dawn's argument is like. If they still choose to enter the fray then they should already know what to expect.
I tend to agree with Chiroptera that as long as Dawn restricts himself to the thread he initiated to put forward his own position on the question its better for him to stay there and run in circles than take his logical propositions into other threads and derail them. People obviously want to bang their heads against a brick wall, given how popular the thread is, so what purpose does banning Dawn, who on his own constitutes one entire side of the debate, serve other than to create a brief hiatus in the proceedings.
TTFN,
AW