Judging by comments and discussions I have come across on blogs in the past month or so, most people assume the axiom to be true, particularly in reference to the birdemic. Regardless, the very notion of good intentions leading to hell has never made much sense to me; not even when I offhandedly used the expression myself in the past.
A good way to test the soundness of any axiom is to reverse it or consider it from the opposite perspective. If the road to hell truly is paved with good intentions, then this implies that the road to heaven must be paved with bad intentions. In other words, if hell is a guaranteed outcome of good intentions, then we should simply abandon good intentions altogether and focus instead on bad ones in the hope that these would lead us to somewhere other than hell.
Saying good intentions eventually lead to hell essentially amounts to little more than a materialistic cop out, one based on wrong assumptions about what defines good as good and bad as bad. Let's reduce these definitions to their simplest possible forms: good is anything and everything aligned with God and Creation; bad is anything and everything that is unaligned or misaligned with, or directly opposed to God and Creation. It really is that basic.
No good intention completely aligned with God and Creation can ever end in hell. Not one. Sure, the intention might not yield the expected result, or it may create perceived unintended side effects, or the action the intention inspired might fall short, but none of these outcomes, regardless of how negative they appear, can be interpreted as hell. Spiritual learning forms the core of our mortal lives in this world; thus, any 'unsuccessful' result of a wholly good intention, one aligned with God and Creation, must be understood as an opportunity for learning. As such, its general direction, movement, and potential is geared toward heaven rather than hell.
On the flipside, 'good' intentions not aligned with God and Creation are bad by default through the elementary error of failing to account for basic metaphysical realities. For instance, many modern people regard twentieth-century communism as a prime example of good intentions leading to hell. Although most modern people are averse to communist methods and means, they are, at the same time, sympathetic to the 'good' intentions that drove communist murder and terror. That is, modern people regard things like equality and social justice as inherently 'good' things that would make the world a better, fairer place. Unsurprisingly, modern people do not question the 'goodness' of these failed good intentions, despite the hellish results. Instead, they tend to view the good intention failures as learning opportunities, very much the same way serious Christians view the outcomes of good intentions as learning opportunities.
But here's the catch - 'good' intentions like the ones that inspired communism were never good - they only appeared to be good. And they only appear good once God and Creation - once Truth, Beauty, and Virtue - are taken out of the equation. Reinsert God and Creation into the mix, and the badness of well intentioned socio-political-economic movements and philosophies are immediately exposed. Yet modern materialists vehemently refuse to take Truth, Beauty, and Virtue into consideration when estimating the morality and virtue of their good intent. As long as materialists believe in a good outside of God and Creation, they will be incapable of learning. As a result, their intentions are fueled by Lies, Ugliness, and Vice; that is, the motivations can never achieve their desired objectives because they are always pointing in the wrong direction, right from the very beginning.
Good intentions aligned with Truth, Beauty, and Virtue are always aimed at the proper objective - and that objective is ultimately heaven. It makes little difference if the intentions do not create the expected outcomes or achieve the desired objective at the temporal level. What matters is that the intentions move us closer to heaven spiritually. All serious Christians know heaven is not to be found and cannot be found on earth. Simply believing it can be is a grave sin. Thus, a perceived temporal failure will always result in spiritual success if the intention driving the intent was sincerely good.
Materialist good intentions are never aligned with Truth, Beauty, and Virtue and are always aimed at a bad objective. Of course, material motivations may contain flecks of Truth, Beauty, and Virtue, but at their core, they align with Lies, Ugliness, and Vice. Unlike Christians, materialists believe they can create heaven on earth. In fact, they not only believe this to be true, but also believe it to be man's duty on earth to do so. This sinful attempt to create heaven on earth rests at the core of all materialist 'good' intentions. By perpetually attempting to do the impossible for the sake of their noble motivations, materialists all but ensure that every single one of their good intentions will inevitable create hellish conditions on earth.
Materialist 'good' intentions automatically preclude any chance of spiritual gain. What spiritual gain can be had if one's intentions oppose God and Creation? In addition, they also preclude any chance at real learning. Materialists will never surrender their misguided 'good' intentions to create heaven on earth, regardless of how many disastrous attempts it takes. Consequently, every pursuit of heaven based on their 'good' intentions will indeed inevitably lead to one place and one place only, but the final destination is not a result of 'good intentions', but rather the result of bad intentions masquerading as good ones.