The Boeotians, of which Thebes numbered, had a widespread reputation for buggery (so did the cities of Chalcis and Sardis) for which the Athenians held them in disdain. And the Athenians got most the press. How much of it was real is anyone's guess. Different times, different mores.
If anyone is curious about my sourcing, it's Michael Grant's Rise of the Greeks - Phoenix Press, 2001, but I think it was originally published in 1987. I'm doing some crash reading for a Greek Civilization course I'm taking starting next month.
Ancient Sparta was an elitist gang of pederasts who enslaved as many of their neighbors as they could get their hands (a nice change) on. Thebes was nominally on Sparta’s side in the Peloponnesian War against Athens, but after Athens was defeated and its wall torn down, Thebes began to assert itself. Within a few decades the jackass king Agesilaus got Sparta to go to war *again* with Thebes, and convinced his co-king to lead the charge while A stayed home with the kids (ahem). The Battle of Leuktra was the best victory ever won in ancient Greece, destroying the last Spartan army; the Thebans proceeded to march around the formerly enslaved areas and set up fortified towns for the locals, ending Sparta’s hideous slavery-based economy for good.
But of course, yes, classical Greece and Rome didn’t really pay that much attention to homosexuality, even among leaders — the decline of the Roman Empire began with the accession of the flaming queen Hadrian, who succeeded the great conqueror Trajan, leader of the Roman Empire at its peak. The difference was, Sparta’s monstrous system made child sexual (and physical abuse beginning in infancy) compulsory.