"Overpopulation" is one of them. "Gay" is another. You can insist on calling yourself gay out of a stubborn refusal to let language evolve, but unless you are gay, you will be giving a lot of people the wrong impression.
The word "overpopulation" (which remains vague and poorly defined) has fallen out of favor and is rarely used in polite company. We can thank, at least in part, those who called for an increase in death rates and draconian restrictions on childbirth for that. They provided the fuel needed by hatemongers like Ann Coulter to make comments like, "We believe in populating the earth until there's standing room only, and then colonizing Mars."
It has also been interesting to watch, over the last 30 years, organizations like ZPG change their names (Population Connection) and evolve into, basically, women's reproductive-rights organizations, joining ranks with NARAL, NOW, and Planned Parenthood. Having won the struggle for lower fertility rates, these organizations now fight a running battle to protect past gains. Read this article from the Associated Press to see how well that battle is going:
Abortion access in many states is being curtailed, activists are uncertain about the stance of the U.S. Supreme Court, and South Dakotans vote Nov. 7 on a measure that would ban virtually all abortions in their state, even in cases of rape and incest.
Correction: The original post said that NPG [not ZPG] had changed their name.