Yeah, but why should duty and responsibility be compelling without higher principles?

Who said anything about a need for compulsion?

According to Hitler, we live in a world where millions accept the principle of celibacy of their own free will, without being obliged or pledged to do so by anything except an ecclesiastical precept. (Celibacy isn't a higher principle, of course.)

Then he proposes dropping such demands and just appealing to common sense by means of reason and persuasion: "Why should it not be possible to induce people to make this sacrifice if, instead of such a precept, they were simply told that they ought to put an end to the original sin of racial corruption which is steadily being committed from one generation to another."

Duty and responsibility are not forced onto people by Nature, but rather, by artificially designed civilization. In the natural order, labour is never looked upon as burdensome and is embraced as a necessity and delighted in. If animals start to exhibit laziness, that's usually due to them being spoiled by humans.

Of course that doesn't apply if you believe in spirituality. You are then required to conform to higher principles.

Higher principles are not confined to a belief in hereafter and god, but include reverence for higher worlds, for natural territories, for laws of nature, for parents. There are many more skeptics who abide by their principles than there are religious believers and ascetics.

These latter deceive themselves into believing they conform to principles. When it's actually a matter of policy for appearance's sake (i.e. politeness, virtue signalling).

Higher principles also become corrupted from the weight of external constraints (conformity, compulsion, conventionality), in a word: dogma. That you value such constraints so highly indicates to me that you're not really acquainted with the inner life.

Even if there was no god and hereafter, instinctive striving and reason would still exist. The animals (birds excepted) know neither god nor hereafter, that doesn't prevent them from exercising restraint in their breeding.