Anyone who says anything but "no cost to save the planet (from destruction) is too high" is clearly deranged. Anyone who says "no cost to save the planet (from another song as annoying as 'hey mickey') is too high" is also clearly deranged, in the opposite direction.

The question is: save the planet from what?

If the person believes that, say, life itself is threatened, then they could legitimately infer that no cost is too high. The problem isn't there: the problem is that the belief in what is at stake doesn't match what is actually at stake.

I agree wholeheartedly that we need to be honest about the difficulty of some compromises that we may need to take...but the bigger problem currently seems to me to be that it's hard to get the general public to adopt a sensible evidence-based range-of-possibilities mindset instead of certain doom or it's all fine (neither of which are remotely plausible).