Yes rocketbob population is a very sensitive issue in many ways, as you say for religion and racism, to name just two. All the more reason for wide-ranging, inclusive debate before any changes are decided on. It wont be easy. I would propose we aim for optimum population by reason, information, education and any changes we can establish a reasonable consensus on. This has the advantage of breaking the taboo on this debate and being less controversial but the disadvantage of perhaps not being enough to achieve meaningful change fast enough. Its better than no action at all and allowing problems to build such that we are forced into draconian action by events. The point is on a finite planet and in a finite city resources available are limited and so there are limits to population size and growth rate whether we like to acknowledge them, as you do, or not.
Dont take my word for it. In Sir David Attenborough’s view, there is no major problem facing our planet that would not be easier to solve if there were fewer people and no problem that does not become harder — and ultimately impossible to solve — with ever more. We must find agreed ways to achieve optimum population in cities, countries and around the globe and especially those with already high populations, those with intense impacts and those with very rapidly growing population and impact intensity. See: http://populationmatters.org/
*We [Bristol] have a population of about 441,300 - the largest city in the South West.
*Bristol's population is expected to reach 559,600 people by 2028
*World population reached an estimated 7, 000, 000, 000 ie 7 billion last month.
*2 extra people every second, that is 200,000 each day or nearly 80,000,000 per year is human population growth on this planet - all needing food, water, warmth, shelter and aspiring to have good choices and a decent life.