My own belief is that we can indeed see Kant’s moral philosophy as consistent but that to do so we have to approach it from a radically different starting point.
According to Kant, values are of two kinds: “dignity” and “price”. Dignity is “unconditional and incomparable”, in contrast to price in which trade-offs can be made. Only one thing, however, has dignity: “morality, and humanity insofar as it is capable of morality”, or, as Kant also calls it, “personhood”. Personhood is an aspect of human beings that transcends the empirical realm and makes us, as it were, citizens of two worlds (“so that a person as belonging to the sensible world is subject to his own personhood insofar as he belongs to the intelligible world”). It is from this inner, intrinsic value of personhood that all other values must descend.
Yes, you might say, but how? If personhood is a transcendental inner kernel that all of us carry within us, then it is, it seems, something that can’t be increased, diminished or destroyed. How is it supposed to guide our actions? The immediate answer is that personhood is something that we have an absolute duty to respect. Yet that, of course, might seem to do no more than kick the can down the road in front of us. We know how to respect things that can be violated, like the right to free speech, but how do we respect an indestructible transcendental kernel?
more here.