Humans react differently to the same information based on how it is presented. It seems to me that activists - specifically those on the left - often fail to take this into account.

I almost always agree with those activists. I certainly agree about global warming. But - pragmatically - if your goal is to convince skeptics, you ought to be very concerned about tone. For better or worse, how you tell your story is at least as important as the evidence backing up your story.