Because it is often easy to detect the operation of motivated belief formation in others, we tend to disbelieve the conclusions reached in this way, without pausing to see whether the evidence might in fact justify them. Until around 2009 I believed, with most of my friends, that on a scale of danger from 0 to 10 (the most dangerous), global warming scored around 7 or 8. Since the recent revelations I believe that 10 is the appropriate number. The reason for my misperception of the evidence was not an idealistic belief that economic growth could have no downsides. In that case, I would simply have been victim of wishful thinking or self-deception. Rather, I was misled by the hysterical character of those who claimed all along that global warming scored 10. My ignorance of their claims was not entirely irrational. On average, it makes sense to discount the claims of the manifestly hysterical. Yet even hysterics can be right, albeit for the wrong reasons. Because I sensed and still believe that many of these fierce environmentalists would have said the same regardless of the evidence, I could not believe that what they said did in fact correspond to the evidence. I made the mistake of thinking of them as a clock that is always one hour late rather than as a broken clock that shows the right time twice a day.

Jane Elmer, Explaining Anti-Social Behavior: More Amps and Volts for the Social Sciences

EDIT: In case it wasn't clear, I disagree that "it is often easy to detect the operation of motivated belief formation in others". Also, when your opponents strongly believe that they are right and are trying to prevent a great harm (whether they have good arguments or not), this often feels from the inside like they are "manifestly hysterical".