Aside from its obvious falsehood, the problem is morality. In the absence of any sort of reckoning after death, what is it that could possibly push human beings towards not oppressing one other? Many atheists in Europe and the Anglosphere make the mistake of assuming that morality and ethics would simply be there and remain even in the absence of religion, while the truth of the matter is that whatever morality they have in such lands is from religion. In other words, if there is no transcendent value, you can do whatever you want.
Rationality does not necessitate morality. As Peterson explains, the tendencies of a psychopath are perfectly rational: pure, naked self-interest. A psychopath's thought processes are no more irrational than those of an altruist. If one is not going to be taken to account in the next life, one's actions simply boil down to what one can get away with.
In a similar vein, Imam Muhammad Saeed Ramadan al-Bouti, may Allah have mercy on him, in his theology book The Greatest Universal Sureties, points out that lack of belief in the Lord and the Hereafter also effects one's approach to knowledge and science. The research methods that Muslim scholars have produced in order to verify reports and narrations, as clearly demonstrated in the hadith sciences, is unparalleled, and that is because the scholars who laid down these methods and applied them believed in Allah and the Last Day. They feared Allah and at the same time anticipated His reward. They firmly believed that checking and double-checking the facts would please their Lord and bring them closer to Him.
As for orientalists and western scholars in general, they have not produced a similar method because the incentive has never been there. Muslim scholars would traverse massive distances and bear significant hardship just to acquire one hadith, even if they already knew the hadith, in which case they would want to get another chain of transmission for it. They expended huge effort in that which had no material gain, because their intention was Allah. For westerners, if there is no material or worldly gain, e.g. money, fame, prestige etc., why bother? Expending such effort is simply not worth it. It's much easier for them to stay within their comfort zones, postulate about life and the universe and then fish around for proofs for their hypotheses.
And with Allah is every success.