I think Adams is very wrong here.
I'm sympathetic to his reasoning, since I have followed nutrition closely for the last twenty years, and believe the scientific/media consensus to be much as he described, and even worse than that occasionally, where people who should know better (a PhD teaching a class on nutrition in a community college) claim things that are both factually and obviously wrong ("Low carb diets are bad because the brain can only metabolize glucose" which has been known false for at least 50 years and probably more.) Cynicism, in some cases, is warranted.
That said, I think Adams is letting people off _way_ too easily. You will notice that when people refuse to believe a scientific position they are always (surprise!) advocating a different position more advantageous to themselves, that will not inconvenience them and that does not reflect badly on them or on those with whom they affiliate. They deny climate science not because the poor wounded souls have had their hearts broken too many times, but because the implication is that their lifestyle decisions are having adverse effects on the world, and addressing those adverse effects will be costly; and because (this is important) because the idea of faggy liberal scientists telling them they're living wrong is too much to take.
It is not an accident that the vocal opponents of things like climate change, global warming, animals welfare, pollution, etc., are the same folks who are 100% convinced that they sometimes get personal messages from angels. Their idiotic worldviews do not arise as a result of Bayesian discounting based on having received bad advice, but from intellectual laziness and an inability (or unwillingness) to look in the mirror and see a possible problem there. (And the aforementioned affiliatory thing about faggy liberals.)