we're talking about a moral outlook that considers it acceptable for a full-grown man to marry a teenager half his age
What IS wrong with that, given their social context? Here we get into silly quibbles about perceived wrongs of different societies, but I'd suggest the behaviour of Western men is no better in this particula rregard, as any man who could would gladly "land" an 18 year old...or is that just culturally-inspired clap trap that the average Western male engages in for sheer sake of feigning Machismo? I doubt it.
The bottom line is, when it comes to law and order, and maintaining justice, the West is ahead. That in and of itself doesn't admit to any kind of moral superiority, as that is highly subjective. I mean, once can easily cite how ludicrous it is that the West allows the "murder" of a baby fetus all in the name of "liberation"...some would reject that outright as hyperbole and others consider it an example of ongoing genocide.
Any other comparisons are neccessarily absurdist, and only pander to those who think that there is some kind of baseline that all humans aspire to...people need the same moral framework to discuss what is and is not moral. It IS, obviously, relative.