If being "iron headed" is to be lacking such feelings, then Kant's position is that an ironheaded person could not be a moral agent because such a person would not be rational.

What are we to think of the shortsightedness of the great mass of people who are content to do nothing about it, and even worse, the greed or venality of the rich and powerful who deliberately bar the way to human survival?

It was an important part of Mendelssohn's philosophical and religious view that the traditional rationalist proofs for God's existence should be sound an convincing. Kant thought they were not. So Kant's critique was world-shaking for Mendelssohn.

The species of anti-Enlightenment religion we find among evangelical protestants is far more impoverished, anti-intellectual and downright wretched.

I don't think Kant's theory looks bad to people except insofar as they have misunderstood it (for instance, as heartless and ironheaded, or as committed to an absurd metaphysical conception of freedom that violates Kant's own philosophy).

The moral law is simply the way we think our own freedom as self-determination.

If we decide rightly what to do, or use a correct procedure for making such decisions, that has to be because the decisions or the procedure rest on good reasons, and these reasons consist in the apprehension of truths about what we ought to do. Because these truths must constitute reasons for our decisions, and because in the rational order, reasons must always precede the decisions based on them, the truth conditions of claims about what we ought to cannot be reduced to, or constructed out of, decisions about what to do, or procedures for making such decisions.