The standard liberal objection to religious motivations for political action is that they are unquestionable and not susceptible of disproof, so that they cannot form a part of the ongoing rational dialogue that should ideally characterize the political process. Indeed, the “special relationship” that secular liberalism posits between religion and violence is based precisely on the fact that religiously-motivated actions are not motivated by reason and hence are arbitrary and unpredictable — i.e., violent.
In one of Zizek’s weakest books, On Belief, he claims that liberals are actually the “believers” in this sense. He doesn’t back up this claim very effectively, choosing instead to indulge in misleading, “provocative” violations of liberal pieties, yet I think we can see that the core insight is there when we notice that the signature gesture of our ruling classes is to present themselves as the mere vessel of impersonal, ineluctable forces. Powerful, impossibly wealthy businessmen have no freedom of choice, as the market determines everything they do. Politicians are similarly guided by what is “politically possible,” irrespective of the range of options their office should theoretically give them.
Obviously it is human to try to beg off responsibility by pointing to forces beyond one’s control — but surely never before in history has a ruling class so thoroughly legitimated itself as constrained by forces beyond its control. It’s as though the one qualification for political or economic power is the ability to divine the messages coming from these powerful occult forces that guide our lives. Any actual deliberation about what should happen is radically foreclosed by this stance: indeed, proposing to debate openly about the shape of our shared life is painted with the same brush of fanaticism as in the liberal critique of religion, except this time the label is “populism” (a catch-all term that completely ignores the unmistakable differences between right- and left-wing principles and priorities).
I would venture to say that back when societies were structured according to religious principles and everyone basically believed in God, a political or business leader who claimed to be a direct channel for God’s will would’ve been regarded as either insane or dangerously disingenuous. Re-label “God’s will” as “the market” or “the politically feasible,” however, and no one bats an eye.
I’d further claim that in settings where religious authority factored significantly in the political process, debate was actually much more vigorous — just compare the Talmud to the editorial pages in a mainstream newspaper, for example. That’s because everyone recognized that the sources of religious authority, as was fitting for something from a divine source, were difficult for us mere humans to understand, so that our conclusions about God’s intent were almost always subject to error and reinterpretation.
Not so with the contemporary impersonal deity who inspires our ruling elites! It’s always right there in the numbers, in black and white. There’s no room for interpretation or debate, unless that means using more sophisticated (and hence reliable!) mathematical tools — at the end of the day, all you need is a literal interpretation and you’re good to go. No religious fundamentalist can possibly be as closed off to alternatives as the secular liberal fundamentalist armed with absolute mathematical necessity.