It's also completely self defeating. Children tend to end up adopting the values of their parents over time. If climate people just remove themselves from the gene pool, their impact on the climate is going to be negligibly small, but there being that many fewer voices of similar values in the future, will have a much more significant impact.

Imagine you're a hyper-partisan and you learn that 'the other side' is spreading messaging amongst themselves encouraging each other to not have children. You're going to be doing backflips, because it's just the collective suicide of an ideology.