I think you're right that what the terminology conjures in the mind is important. And, it can be tricky to communicate some of these ideas positively. For instance, the phrase "reducing the population" is probably as unpalatable as "eugenics" for some. It does sound a bit callous; as if we are saying that we want/need people (i.e. members of the existing population) to die.

Even phrases like "population control" and "population management" carry this negative connotation. There probably needs to be a new, friendlier term. Something positive-sounding like "right-sizing" or "harmonizing".

In short, these ideas need better PR.