OK. So @BeckyAMumsnet you seem to be saying that we are allowed to challenge or request evidence once, but we aren't allowed to ask again or point out that the poster hasn't provided the evidence requested?
When I have reported disinformation previously, the moderators have told me that MN can't determine what's true and what isn't, but we should feel free to challenge disinformation on the threads.
What you now seem to be saying is that we aren't really allowed to challenge on the threads in any meaningful way after all, because posters will just ignore the initial challenge and carry on posting whatever nonsense they are eager to promote. In other words, disinformation must be allowed to stand.
As for saying "I disagree because...", that is not always possible when someone has made a very vague sweeping statement without any evidence - hence the need to ask for evidence so the the point can be properly debated.
Sadly, it seems that you are confirming that MN is no longer a place for robust and rigorous debate where people can actually be challenged effectively and held to account for what they say, because we are all expected to pretend that everyone is here in good faith and that all posts are equally valid.
What a shame.