Pederasty in ancient Greece, did they get it wrong, or do many nations have it wrong today?

Part of what it says of pederasty, for those who never heard of it, ”The rite of passage undergone by Greek youths in the tribal prehistory of Greece evolved into the commonly known form of Greek pederasty after the rise of the city-state, or polis. Greek boys no longer left the confines of the community, but rather paired up with older men within the confines of the city. These men, like their earlier counterparts, played an educational and instructive role in the lives of their young companions; likewise, just as in earlier times, they shared a sexual relationship with their boys. Penetrative sex, however, was seen as demeaning for the passive partner, and outside the socially accepted norm.”

”The age limit for pederasty in ancient Greece seems to encompass, at the minimum end, boys of twelve years of age. To love a boy below the age of twelve was considered inappropriate, but no evidence exists of any legal penalties attached to this sort of practice. Traditionally, a pederastic relationship could continue until the widespread growth of the boy’s body hair, when he is considered a man. Thus, the age limit for the younger member of a pederastic relationship seems to have extended from 12 to about 17 years of age.”

Were the Greeks wrong or did they have it right, and how would you determine they were wrong apart from simply having superior numbers supporting one stance or the other? Cultures have their own acceptable norms for sex and intimacy be it pederasty, so-called child brides, etc., or some other non-westernize form of sexuality, at the crux of the biscuit, isn’t it just an act in another culture? How will sexual practices of today be viewed 300 years in the future (if mankind last that long)?