This has come up in other threads and some posters decided we should post cute animal pictures when the non/anti-childfree post stupid or inflammatory comments. IMO that's not very helpful as it derails the thread just as effectively as the invaders.
So in site stuff I asked MNHQ if we should bother reporting posts like "why are you on a PARENTING FORUM" and "childless people are so angry and bitter" - just two examples of the many irritating comments we've already had multiple times on our board.
https://www.mumsnet.com/talk/site_stuff/4841580-threads-showing-on-active
Mumsnet replied: It's definitely worth reporting those sorts of posts. If it looks like someone is being deliberately inflammatory, we'd see that as reason to take it down, particularly if they're continuing having been asked politely to desist, or doing this sort of thing repeatedly. We can also post on those threads ourselves, if that helps, to point out that Mumsnet is a forum for everyone. Do just drop us a line where you see this sort of thing and we can take it from there.
We'd much rather tackle that sort of posting at source than take a board out of active, particularly such a new board, as it means fewer people will happen across it and it may simply fizzle out, which would be a real shame.
So when they turn up, those who want to can post cute animals and others can ask them politely to stop and then report any further posts. If a thread is being particularly derailed, we can ask MNHQ to post a reminder on it.