Anyone old enough to remember who Kennedy was is (a) unlikely to buy this tired image of a Gandhi cum Churchill folk hero and (b) not go to be around in 2050 to benefit from reduced carbon emissions.

You say: “..the environmental movement is incapable of turning its values and principles into an appealing vision. It cannot create a grass-roots movement”.
But they don’t have to, if they can capture hearts and minds of the chattering classes, and hence the policy makers and political parties, via their control of the BBC and serious press.
And you finish: “Fortunately, nobody is really buying it”. Nobody except the UN the EU, and practically every political party in the western world. I’d like to share your optimism that the common sense of ordinary people will prevail, I really would.