> You're not seriously suggesting humanity is better without the Internet…

I cannot speak for karaterobot, but that seems to be an unwarranted inference from the post you are replying to, which merely points out that the internet did not lead to the more cooperative and altruistic world that some idealists predicted.

You posit that humanity would step up to the challenges of a ten-fold increase in longevity, but I haven't seen what I would regard as persuasive evidence for that view. The fact that the internet has been a net benefit (a view I accept) is not that evidence, IMHO.

The argument by analogy, as I understood it, was the following.

  Internet idealism : Internet negatives¹ :: longevity idealism : longevity negatives²
  ¹flaming & porn ²scarcity & overpopulation

In the context of a discussion about whether or not to undertake a societal change (widespread longevity), bringing up an example of a prior societal change (The Internet) where the result didn't live up to the ideal is more likely than not an argument against making the change in favor of maintaining the status quo (killing statistical 72 year-olds).

Statistical 72 year-olds? What are they? And the status quo is that they are killed? You appear to be inventing some bizarre argument that has not even been mentioned up to now.