To be accurate, Constantine did not make Christianity the official religion of the empire. That happened decades later under Theodosius.

My argument is that you cannot avoid religion. Even if you try to adopt an atheistic perspective, the result is that the state becomes the new god. And more oppression and death occurred under atheistic regimes in the 20th century than in the rest of human history combined.

At the end of the day, all law requires a law-giver. If we say that law is just determined by a majority vote, that is no guarantee of justice. If it is just an evolutionary process, then it comes down to might makes right.

God’s law provides for genuine freedom and recognizes human rights because man is made in the image of God. But if man is just a product of a blind evolutionary process, then humans are just a bunch of fizzing chemicals and are of no more inherent value than a mosquito. In a cold and impersonal universe, there is no such thing as rights, or even right and wrong for that matter.