"Iraq had WMDs in 2000s" != "I strongly believe Iraq had WMDs in 2000s" != "I find it plausible that Iraq might have had WMDs in 2000s" != "According to that UN report, Iraq had WMDs in 2000s" != "According to NYT, which quotes that UN report, Iraq had WMDs", etc.
A lot of problems are caused by people who say "X" when they should say "I strongly believe X", or "I think I read somewhere that X", or "I'm not sure, but I think X".
Once you've set the bar re: certainty for a particular discourse neighborhood, you can just make claims at that level thereafter without feeling dishonest. As long as you're sensitive to cases where others may have joined without enough context to know that you're out on a limb.
It's depressing.
This is Circle of Competence applied[0]. It's admitting what you know you don't know so you don't make mistakes by being overconfident.
So, for instance, if 'tptacek here says a factual statement about security (and there's no large thread contesting it), I'll treat it as gospel. But if he says he's unsure about it, or he read it somewhere, I know to attach less weight to it. I'll code in it my brain as "uncertain, but passed the sniff test of a relevant expert". Etc.
The same principle works in more mundane aspects of life. Whether a person believes something (and how much), or whether they're just reporting something they've read elsewhere, matters a lot for evaluating a factual statement independently.
You left out the last step,
!= Bush administration says Iraq had WMDs
Except for that for a lot of "facts", according to Rousseau, we already have 4 truths: what you say, what I say, what we agree upon and what really happened.
So, while the pursuit of truth is important, I'd argue that respect towards each other even when we cannot agree is the most important thing.