Do you mean that we often encounter social/political explanations involving entities for which no strong evidence exists, or the less trivial one that social/political explanations often involve (not explicitly supernatural) ontologically basic mental entities?
But why should the mental quality of the postulated entities be such a big deal?
Note that in the context of ideology and politics, the critical question is not so much about positive explanations of phenomena, but about normative justifications. And in this context, I really don't see why one should privilege justifications whose metaphysical element happens not to include any antropomorphic (or as you say "mental") entities.
For example, what is supposed to be so much more irrational about semantic stop signs that say "X must be done because otherwise we'd violate God's commandments" versus those that say "X must be done because otherwise we'd violate human rights"? (Of course, it may be that you mostly prefer those concrete Xs that happen to be justified the latter way in the present public discourse, but surely it's not difficult to imagine an opposite hypothetical situation, i.e. one where people justify something you otherwise favor by invoking God's commands while others justify something you oppose by invoking human rights.)
I had assumed that the explanations we're talking about were positive or causal.
When it does come to normative explanations in everyday life I don't think the implied metaethical framework is particularly interesting or important, given how humans actually make decisions and employ concepts. Obviously, read literally any reference to external, not-merely-intersubjective entities like "human rights" are as silly as references to God's commands, and if we're having a discussion about philosophy they can be dismissed with exactly the same anti-supe...
I've recently run across this 2007 post on the blog Unqualified Reservations (archive best read here). It is written by Mencious Moldbug, who is probably familiar to some Overcoming Bias and Lesswrong readers. He is a erudite, controversial and most of all contrarian social critic and writer. In 2010 he debated Robin Hanson on the subject of Futarchy.
Violating Godwin's law to breach the fence between religion and ideology to see what cognitive dissonances we can dredge up is old hat for us LWers (A Parable On Obsolete Ideologies 2009 by Yvain).
I hope you can now see reason I've picked a partially misleading title, since I think Moldbug makes a pretty convincing argument that belief in "religion" may be considered harmful even for atheists, let alone those of us who aspire to refine rationality.
In such a model questions like "is the Church of Scientology a religion?" dissolve rapidly. Whether something should be tax exempt because it is "really" a "religion" or "a church" is a legal question of importance only to activists trying to challenge law and lawyers, that shouldn't change our ethical intuitions or cause us to try to imagine a sea or play up rather minor geographical features, to separate the continents of Religion and Ideology in our maps of reality.
Every single proposed mechanism for the retention and spread of religion from convenient curiosity stoppers, indoctrination of youth, to tribal identity markers hold for ideology just as strongly as for religion. Even seemingly very specific memetic adaptations like "God of the gaps", seem to arise in various non-theistic ideologies. Maybe similar adaptations arise because it is the same niche?
Thinking about the implications of such a hypothesis, atheism for one additional god is a rather easy step of rationality to take. Very few people believe in the great Juju or Zeus. Adding YHWH to the list isn't that much of a stretch, for those fortunate enough to be educated and living in most of the West.
But how hard is it for someone to question, in a unbiased fashion, such gods and holy words such as say Democracy?