If you have a look at the evidence, there's a strong case to be made that the real problem is not population numbers but, rather, rates of consumption and, most particularly, the consumption of a narrow sector towards the top of society.
I don't think many would argue there aren't probably too many people on the planet. The question is what do you intend to do to change it? As I see it, these are your options;
A. Enforced euthanasia on a criteria of your choice (e.g. age, disability, fitness, race, religion, intelligence)
B. Mass sterilisation of young people on a criteria of your choice (e.g. disability, fitness, race, religion, intelligence)
C. Voluntary euthanasia (will this make up the requisite numbers?)
I don't think many would argue there aren't probably too many people on the planet. The question is what do you intend to do to change it? As I see it, these are your options;
A. Enforced euthanasia on a criteria of your choice (e.g. age, disability, fitness, race, religion, intelligence)
B. Mass sterilisation of young people on a criteria of your choice (e.g. disability, fitness, race, religion, intelligence)
C. Voluntary euthanasia (will this make up the requisite numbers?)