I think that environmentalists have received a bad rap for the accusation of only having one rhetorical tool, the "I Have a Nightmare" argument, in contrast to Martin Luther King Jr.'s "I Have a Dream" rhetoric. One thought I had that might prove the bad rap was to look at what King himself had said, because I suspected there was a fair amount of nightmares in King's speeches.
So I borrowed a library book with King's speeches and checked the dream to nightmare ratio, first in the original Dream speech, and then in a eulogy for the schoolgirls that were killed in a church bombing. It didn't back up what I thought I would find. His Dream speech had about twice as many hopeful lines as it had fearful lines. Even the eulogy for the murdered schoolgirls was about equal in the dream to nightmare ratio, talking about the girl's happiness in the afterlife and the hopes that their sacrifice would instill to work for a better future. Other speeches I skimmed were similar. King definitely emphasized hope over fear.
I still think the Nightmare rhetoric of activism is an essential one, pointing out the problems that will occur if things are not changed, but King's hopefulness is also something to remember.