Seriously though, with governments already deciding that their targets are to reduce emissions etc by less than 50%, it is apparent that a reduction in population by 50% would, even at current emission levels per capita, achieve the target. Equally, half as many people will need half the resources for feeding (less than half if the fattest have been "dealt with".) This is why it is obvious that the solution has to be fewer people. If you care about the planet but don't believe people can be educated into preferring hedonism to breeding, then keep your fingers crossed that the next pandemic does a proper job.
There is absolutely no way that any government is going to set targets of reducing emissions by say 50% of current levels by, say, 2030 by setting targets of reducing population size by 50% (size not recruitment). Even Russia or N Korea would struggle (you would hope).
I really don't follow your logic. Of course we agree that there are way too many people, but even with vastly reduced breeding the numbers aren't going to come down much in the foreseeable future. And if they were to be reduced marginally in some places (say Italy or Japan) there will be other places where they go up.
Your argument that any crisis in animal extinctions is solely/ultimately/mostly caused just by their being too many people strikes me as similar to making the same argument about global warming - the only cause is there are too many people. Of course it is the root cause. 100% . However global warming is caused along the way by a number of other factors such as deforestation and a major one of emissions. You seem to be saying (as a parallel example) that reducing emissions won't solve anything* and thus we shouldn't do anything about it. In environmental terms that is akin to suicidally burying your head in the sand? There would be no effort to reduce emissions, no effort in alternative energy supplies or reducing deforestation etc etc.
There is (and has been for some while) a global crisis in foodstuffs feeding the population of humans.
Of course you can eat as much meat as you want to at a personal level (as can I, I'm not a vegetarian either), but globally it's worth looking into the whole picture. (Going back to the original paper that includes bushmeat, competition, bycatch etc in addition to farming)
*(Being cynical, yes, but that is a) defeatist and b) woefully ignoring the problem)