OK - we were called the anti-dementors and it originated (and I hate to burst the OP's hate-bubble where they've decided better than those who coined the term) from the Harry Potter books after a thread where someone expressed that they were being really emotionally worn down by those who would take any glimmer of joy and absolutely flip it around to the depths of Covid doom - in some kind of fucked-up Monty Python Three Yorkshiremen sketch type of the way.
So "oh we did our home learning in the garden today because I'm sick of the house" would be turned around into a tirrade of how dare you go out into the garden, don't you know there's a pandemic on and people are dying and what if Doris is on the other side of the hedge over at number 57 and you might be incubating covid and breathing and kill her and then she'll never get to cuddle little unborn Daisy at her 28th birthday party get together. Someone commented that it felt like every glimmer of (even covid-"allowed") joy was being sucked out of the world by some on here - like the Dementors in Harry Potter - and THAT is where the term came from.
The linguistic origins of where JK Rowling took the term from is totally different to where the origins came from on MN which was very firmly from those residents of Azkaban.
Off the top of my head we were called:
Granny killers
Covidiots
Anti Vaxxers (for the record - I had the first two jabs and I still suffer from vaccine side effects, which I'm fairly resigned to - someone somewhere's going to get hit with the shitty side effect stick of anything - I just fought for the right not to be mandated to have any more and make things worse)
Right wing Trump supporting loons - that one came up a fair bit - quite how someone in the middle of the UK is meant to be a Trump supporter is interesting
I believe we were also accused of being on the payroll of UsForThem at one point and therefore would be uber rich right-wing extremists (skint, left wing, sorry to disappoint)
We also diversified into mooncup logistics, dodgy shaped vegetables, soup recipes (have a corking smokey bacon and vine tomato one that DH does now incidentally), strategies for going to Tesco and sitting reading a book in the carpark pretending the queue was horrid so as to get a bit of space alone... and lots of other sidelines to the granny slaughter. I don't quite know why we never got accused of grandad slaughter - it was always the grannies.
And yep, I take the piss openly over the suggestion of putting cheese in coffee because it was bloody ridiculous and I've not got round to thinking of a different username yet or bored enough to get round to do it.
We had ONE THREAD going - replaced when it hit nearly full - you had an entire sub forum and took over most of the site. @MNHQ @HopeMumsnet come on sort this out cos this is bloody bullying.