I think his point was that cost-benefit analysis is subjective. Your supposition that it's not limited to monetary concerns alone is valid, but perhaps naive. The fact that most people don't do a "proper" analysis is the very nature of bias.
If you talk to many environmentalist they see it very much as a moral argument. Perhaps it's a different moral level for many of us, but not to everyone.
As such while his argument used an extreme example, I would not consider it as nonsensical.
If you talk to many environmentalist they see it very much as a moral argument.
And that's the problem. They may as well have a Bible in their hands and go knocking on doors.
More people can be swayed by explaining that a particular action has a direct benefit and is therefore more effective than the current one than by saying "repent for the end is near" and "you're a backwards hillbilly who is evil for not seeing this my way".
If only that were the case. If there is anything that the modern environmental movement has taught us, it is that religeon is a powerful force regerdless of whether it includes gods or targets academics. For a more nuanced (and defensible) discussion of the topic, refer to "Environtemanetalism as Religeon" by Michael Crichton: http://www.crichton-official.com/speech-environmentalismasel...
If you talk to many environmentalist they see it very much as a moral argument. Perhaps it's a different moral level for many of us, but not to everyone.
As such while his argument used an extreme example, I would not consider it as nonsensical.