The problem with this:

While increasing suicides suggest things are getting worse, if one cares for the environmental destruction due tom overpopulation, both abortion and suicide should be supported.

…is the game theory. If you do things as a culture to reduce your own population, but another culture doesn’t, then your culture dies out and their culture prevails, with its indoctrinations about population control.

FWIW, this was one of the few things the NZ shooter got right in his manifesto, even though he didn’t explain it particularly clearly, and he gobbed it all up with “white genocide” claptrap.