Well, I agree that forms of progressivism can end up being totalitarian and counterproductive. This is largely a question of intellectual integrity or of self-knowledge. The question is whether we're clear on the implications of our ideology.
Often, whether we call ourselves conservatives or liberals, we use rhetoric to obscure what we really want and who we think we are. We do this to sell ourselves and our plans, so we end up perpetrating cons. That can happen in all walks of life and on the left and the right. We have primitive, tribal prejudices and if we don't consciously counteract them, they carry the day and seep into our grandiose ideals and self-conceptions, despite our stated intentions. It's a question of hypocrisy or self-delusion.
You seem to be lumping bureaucratic, "evidence-based approaches" in with scientism. If you're talking about the sort of skepticism you find in Adam Curtis's documentaries (or in John Ralston Saul's Voltaire's Bastards), for example, I share that skepticism. I've written a lot about that. I take certain lessons of existentialism to be opposed to that conceit of hyper-rationality. That led me to argue against new atheists, for example, on behalf of the "old" ones.
But I'm not sure you're clear on what I'm arguing here. The value of the relative-absolute conservativism distinction is just that it facilitates self-awareness and undermines the con.
Take, for example, the law you speak of, about keeping the defendant's record away from the jury. That law is meant to promote objectivity and a fair verdict. Yet those very values (objectivity and fairness) are antithetical to the type of society that tends to be produced by conservative policies, regardless of the conservative's rhetoric or salesmanship.
The masses are oppressed by the excessive power of the elites that arise in a monarchy, plutocracy, or dictatorship, and the elites rationalize their privileges with myths that run contrary to objectivity. Moreover, the whole system becomes massively unfair (amoral, animalistic, and a waste of human potential).
So I'm talking about the incoherence of half-assed conservatism. And the coherent kind of conservatism, namely animalism or social Darwinism, is patently monstrous in contrast to humanism (although humanism isn't necessarily a recipe for utopia either).