The major problem with 'challenge it on the thread' model of dealing with disinformation/problematic posts which MNHQ rely in is that it relies on people who aren't paid to do a fucking awful job.
It's not a case of 'oh you've got your facts wrong, vaccines don't cause autism' (to deliberately pick an example entirely disconnected from this thread), and the poster retreats in shame, it's a case of having to post over, and over, and over repeatedly on different threads to posters who can be increasingly belligerent and insulting 'oh so you're happy for babies to die'. The posters can also as well as being obnoxious, be extremely persistent and prolific (particularly the astroturfing type).
So people give up, and the 'challenge it on the thread' model becomes 'this shit is totally left unchallenged because no one left can be arsed' model. It's particularly bad when you - as someone who has been incredibly involved in this topic - knows when a poster is prolifically posting in bad faith, report to MNHQ and say 'this poster needs looking at' and you get the 'thanks for your post, we are looking into it' and them absolutely nothing happens.