Ask them what became of phrenology and phlogiston. Both had widespread scientific support. Also, what became of the ether through which light was supposed to propagate. Ask them why Wagoner died discredited because of his crazy notion of plate tectonics that all geologist knew was false. Finally ask them if they know the story of Galileo and how he spent his last decade or so.
Science is not a popularity contest and consensus is of little importance.
That is true, but there is a great deal of coherence in the "thicker blanket" analogy of CO2. Are your friends warmer at night with a thicker blanket? Sure, that's not a religion, just a fact. The salient issue is how much warmer. Even counting the 80's and 90's warming, some of which was known to be solar, the world is warming 1.3C per decade according to satellite, the best measurements we have.
See http://www.drroyspencer.com/latest-global-temperatures/ Lately the rate is more like 1C per decade. That is a benign rate of warming and like I said before, the ocean cycles and solar slump currently point towards cooling. It is likely that we will see that chart roll over.
One more thing to add to address chicken little fantasies. Lots of "extreme" weather events have no trend or even a downward trend. The trend in strong tornadoes is down over the last 50 and the last 100 years. We are in the longest period on record without a najor hurricane hitting the US (although that is mostly luck). All those facts and more can be easily found with google (just add WUWT to your key words).