I wouldn't qualify those in favor of death as misanthropes, they have a very valid point, even if some have it for the wrong reasons. Humanity is not ready for the wealthy to live forever. They say science advances one funeral at a time, and that is true for all of humanity.

Political, legal, and economical systems would have to be prepared before that, otherwise countries would stagnate as undying parasites embed themselves in society for centuries. As they won't want competition, the most effective antiaging treatments would be priced out of the commoners forever. In some countries like USA people struggle to pay for insulin, much less antiaging treatments.

Edit: regarding your question, if people lived naturally forever, and it became a problem just recently, I think they're already adapted to living forever, and the problems come from something new. Anyway, let's suppose the problems are caused by overpopulation, then the solution would be to limit reproduction, and let the population fall down a bit as accidents/murders happen naturally.