"Seeing politicians use it as a scare tactic also firms up this reaction."
Politicians use everything as a scare tactic. "Socialism!" and "They're just trying to take your guns away!" are two of my personal favorites. Unfortunately, many (most?) of our politicians are not our best and brightest (or, perhaps, even very bright at all), so they don't have much else to rely on to get elected. Plus, let's face it, much of the voting public is pretty, well ..... ignorant. Not quite capable of critical thought. FUD works, and it works well. In fact, it works much, much better than honesty.
Anyway, I think reasoned people, for quite some time, have been warning about global warming without the "world ending tomorrow" rhetoric. IF global warming is a real problem (I think it is, and the vast majority of scientists think it is, but I respect those with opposing opinions when based on science and critical thought) then there's a tipping point. Don't know when that tipping point is. I personally think we're at it or near it.
So ... if the bridge is out, and you keep heading down the tracks toward the bridge at a high rate of speed, early on you can calmly say that you really need to change direction. But at some point, if you just keep barreling down the tracks in the same direction, the message will necessarily get more dire and compelling, and perhaps, just before you go crashing down into the canyon, hysterical.