As with most things in life, Alasdair MacIntyre cuts right through the noise to the heart of things (in this case, what public support for Donald Trump might mean. From the first chapter of Whose Justice, Which Rationality:
Partly it [the Teflon-like ability of some to resist the charge of “irrationality” or “extremism”] is a matter of a general cynicism in our culture about the power or even the relevance of rational argument to matters sufficiently fundamental. Fideism has a large, not always articulate, body of adherents, and not only among the members of those Protestant churches and movements which openly proclaim it; there are plenty of secular fideists. And partly it is because of a strong and sometimes justified suspicion by those against whom the charge is leveled that those who level it do so, not so much because they themselves are genuinely moved by rational argument, as by appealing to argument they are able to exercise a kind of power which favors their own interests and privileges, the interests and privileges of a class which has arrogated the rhetorically effective use of argument to itself for its own purposes.
Arguments, that is to say, have come to be understood in some circles not as expressions of rationality, but as weapons, the techniques for deploying which furnish a key part of the professional skills of lawyers, academics, economists, and journalists who thereby dominate the dialectically unfluent and inarticulate. There is thus a remarkable concordance in the way in which apparently very different types of social and cultural groups envisage each other’s commitments. To the readership of the New York Times, or at least that part of it which shares the presuppositions of those who write that parish magazine of affluent and self-congratulatory liberal enlightenment, the congregations of evangelical fundamentalism appear unfashionably unenlightened. But to the members of those congregations that readership appears to be just as much a community of pre-rational faith as they themselves are but one whose members, unlike themselves, fail to recognize themselves for what they are, and hence are in no position to level charges of irrationality at them or anyone else.
If you believed (with evidence) that there was a conspiracy of “reason” that made the kinds of arguments, beliefs, or reasons you held about a topic to be prima facie inadmissible in public discourse, don’t you think you would glom on to the first person or persons who “told it like it is” or “said what you were thinking”? It is in this way that (in the US, as well as Europe) it is the conspiracy of the “reasonable” biens pensants in the political and media elite to narrow legitimate political discourse that ultimately creates the vacuum into which far right populism enters.