“Ancient Greece was a hotbed of decadence.”
“Decadence” indicates decay or decline. That’s inaccurate because homosexuality and pederasty were normative in ancient Greece during its political and cultural peak. These behaviors were hardly aberrational for the Greeks. Philosophical and political mentions of both are rife, and in mythology there’s the story of Zeus and his cupbearer Ganymede.
While the fighting prowess of the Spartans is legendary, the story of their ultimate defeat by Thebes is much less well-known. Thebes was famous for its Sacred Band of paired lovers which beat the Spartans and made Thebes the preeminent Hellenic power until the Macedonian conquest.
That is one definition of decadent. Here is another Webster definition: Marked by or providing unrestrained gratification; self-indulgent. Decadence is typically used within the context of moral decay. How the Ancient Greeks arrived at a acceptable social norm is not the assertion by me, the CONDITION(decadence definition)of the time was of moral decay. This is affirmed by the apostle Paul who certainly takes on the Corinthian church(1 Corinthians 6:9-10) with their immoral behavior. America cut the path for this.
Secondly, scholars disagree as to the extent of homosexual behavior in ancient Greece as being “normative” as you suggest. Some say that is was a sole exercise of the aristocracy, others not. Read Wikipedia: Homosexuality in Ancient Greece; Scholarship and Controversy, and you can find plenty of scholarship showing ancient distaste for the practice of homosexuality. Even Plato detested it, “utterly unholy, odious-to-the-gods and ugliest of ugly things”
Finally, as much as Greece became the lush fields for the seeds of Christianity and an anchor to part of the Church, today’s Greeks, westernized in many ways have fallen back in to their former idolatrous ways.