You are right in general, but for succinct Internet discussion it is necessary to simplify as much as possible. Unfortunately this can sidetrack the discussion

You are right in general, but for succinct Internet discussion it is necessary to simplify as much as possible. Unfortunately this can sidetrack the discussion as flaws in the simplification are addressed. In the case of humans, evolution did encourage diversity, if only because it created sexual reproduction in humans, which increases the diversity of offspring. And of course, humans are not all identical today, implying an evolutionary response to different environmental conditions.