the interchange i originally quoted did use the argument exactly in the way i described, and it's not the only instance in which i've seen it. and no, all the elements you referred to(and didn't refer to) do not collectively provide proof, because proof is irrefutable by definition. you have evidence. this may seem like semantic nit-picking, but the difference is huge.
as i suggested before, i'm not interested in convincing anyone he did or didn't have AIDS - and i'm familiar with the arguments for saying he did. they aren't absolute, and they rely almost fully on speculation and personal experiences, but it doesn't matter, because that isn't what i'm addressing. circular logic is employed in discussions of this issue, regularly - saying it is a logical fallacy to notice an inherent flaw in a statement doesn't make the flaw go away. which one makes more sense: defending an ineffective argument, or making an effective one?