Population/natural resource exhaustion related crises are a bit iffy, because it is plainly obvious that if they remain exponentially growing forever, relative to linearly growing or constant resources (like room to live on), one or the other has got to give.

Obviously the people disputing the wrong predictions know this. Julian Simon was just as familiar with this trivial mathematical fact as Paul Ehrlich. The fact that this knowledge led Paul Ehrlich to make bad predictions indicates that his analysis was missing something that Julian Simon was considering. Often this missing something is a basic understanding of economics.