I may not represent the majority opinion for these ideologies, because I don't spend my free time in these communities, but I'll try to sum up my thoughts on taking actions informed by this kind of thinking.

Good anti-natalists with any measure of forethought should very quickly come to the conclusion that small scale terrorism doesn't do anything to solve the crisis of new life, or to reduce suffering- which is supposed to be the goal.

Good pro-mortalists, if given the opportunity to solve all suffering once and for all, should very quickly come to the conclusion that regardless of their thoughts on the bigger questions, it isn't up to them or anyone else to press that button or turn that key.

Its delusional thinking to believe that just because you know everyone is probably better off dead, other people shouldn't be allowed to go on suffering, or to bring about another generation of sufferers, if that's what they choose to do.

If you are heavily pro-mortalist, and you think life would be better off dead; Congratulations, the laws of physics are on your side! Every source of heat and life that has ever existed will inevitably be snuffed out and the universe will just be a bunch of cold little rocks, which will continue to get further and further away from eachother until they're eventually just little islands of nothing, in an ocean of nothing, screaming off into nothing.

You win in the end, no reason to rush things.