If you're saying the world is overpopulated by X then you're saying X amount of people who exist shouldn't exist.The observation is that a given population and affluence level cannot sustainably exist. Not as a matter of morality or prescription, but as a simple matter of fact. The concept of overshoot, well established in ecology, is one that specifically notes that populations can for a finite period of time, exceed long-term carrying capacity, but will in time collapse. Overshoot itself --- population in excess of sustainable capacity --- occurs because of lag effects. Consequences of actions follow those actions, but not necessarily immediately.
https://en.wikipedia.org/wiki/Overshoot_(population)
Population dynamics, like diseases, don't distinguish on ethnicity, religioun, ancestry, or ideology. It is true that the poor tend to bear the brunt more heavily. I ascribe no moral justification to this, though theological and ideological doctrines of the past and present very frequently do, to their discredit.
Respondind that a fact may be legitimately rejected simply because its implications are too painful to consider is wishful thinking, the informal fallacy of argumentum ad consequentiam appeal to consequences.
https://en.wikipedia.org/wiki/Appeal_to_consequences
What you are saying is ... well, Col. Jessup had something to say on that:
https://yewtu.be/watch?v=5j2F4VcBmeo
Adding to that error, you then invent the utterly unsupported claim that those making the case for overpopulation mean for any reduction measures to only apply to others. This is in fact entirely a fiction of your own creation in this discussion. It does of course make answering the claim all the more difficult. I point out that as a fabulous claim there is no need to do so.
As I've noted before in this thread, you seem bent on repeatedly dragging this discussion into moral territory, in a manner which makes substantial and productive discussion difficult. It would benefit the discussion, and you might learn something, were you to not do so.