This is a frustratingly common technique that I've seen from those who have strong political affiliations.
It's much easier to make a strong claim, and to repeat it, than it is to read through articles and debunk those claims. Frequently, as soon as you've done it, there are several more of these strong claims made, and the discussion becomes impossible.
I think it's rooted in the desire to "win".
I know I get a little excited when I see a comment I've made get upvoted.
I think about it when I'm writing and I've found it affects what I write and my phrasing.
I think this is an unintended consequence of self-moderated discussions - it seems to devolve into a zero-sum game.