It's about tax
McKinsey are about marketing (and arse-covering), and politics is marketing (and arse covering).
So what they are saying is that politicians can make a case for taxing fat people etc, and the anceint voters will nod and agree, irrespective of the underlying facts, with little risk of burned backsides.
Indeed the whole point is that the argument can be won in the face of facts. Such is the devilry on display here. Nice innit?