Ant-Natalism,
I'm not sure 'how such a group could achieve it's goals. Barring the Big Red Button of an Apocalypse.
I suppose they could try adoption and acceptance of adult converts,
Try to claim some territory and keep claiming territory until they can enforce their belief worldwide.
Seems 'likely to me though, that they'd be outnumbered by people who want to procreate,
Let's say Anti-Natalists took half the world,
Rest of the world might try pretty hard to prevent any of their own from being adopted or converted.
Even within the Anti-Natalists own territory, again I imagine there'd be a population of people 'currently exempt from Anti-Natalist regulations, that the Anti-Natalists have a population to adopt and convert from,
'But groups have their desires for power, rebellion I'm sure.
So Anti-Natalists might 'have to reproduce I think, to successfully hold territory.
. . .
I suppose if an individual saw a drugged or physically deformed person who cared not about their children, kept 'having children,
Some people might think it is better to kill said individual, than let them create another person in painful existence,
I'd 'imagine but not know, that most Anti-Natalists see new people as more of a roll of the dice or as someone one cannot ask for permission to be born, thus wrong.
Besides, odds can be estimated from genetics and environment sometimes.
. . .
People are 'going to have kids I think,
Even if one killed X many people, way of the world I think is that 'other people produce even more to fill that space.
. . .
Eh, killing other people doesn't seem the 'best way to get Anti-Natalisms various goals or messages across,
But Bad publicity is Publicity, some might say.
. . .
Hm, maybe Anti-Natalisms best bet 'would be the Big Red Button,
Gather like minded individuals and power, attempt to create a Doomsday weapon or Doomsday Political Situation.
Though I'm not sure that'd be enough, unless it 'really wrecked the Earth, life finds a way sometimes,
Only a brief peace of the grave before some other species stands on their own two legs, succeeding humans.
That or perhaps humans survive anyhow.
. . .
More achievable for most Anti-Natalists though,
Might be trying to make the world a nicer place, encouraging better genetics and situations, nature and nurture, to try to improve the odds of fulfilled lives for new people.