"I think GoT deals with several different morally grey issues and is anything but insulting or crude."
Marriage and prostitution are two of the biggest, and lets face it, the GoT world is very male-dominated to the point where the only power a woman can wield is sex. Cersei, for example, uses this to her advantage after her arranged marriage to King Robert, but then takes it too far and it ultimately gets her into pretty serious trouble when she tries to use sex against Margaery Tyrell. I think this is why Brienne is one of the more fascinating characters in the book, and even that comes with an asterisk because she rose to prominence under a gay usurper in Renly and the biggest danger she faces as a knight is rape instead of death.
I think the biggest moral issue ASOIAF deals with, especially in ADwD, is slavery.
SPOILER ALERTS
Many of the most important encounters in ASOIAF take place in whorehouses (think Ned meeting Catelyn in King's Landing, Tyrion getting kidnapped by Jorah in Volantis), but I'm torn as to whether GRRM is drawing parallels between the sex trade and the slave trade. What's clear, though, is that the main characters, as Westerosi, look down on slavery as essentially barbaric (except Euron and Victarion) but are entirely fine with prostitution. Despite what SYnapse claims, in the ASOIAF universe, prostitution isn't treated as a "last resort" for many girls. Quite the opposite - it's an escape from the drudgeries of the commoners. Like Cersei, sex is a woman's path to power, and you can see even how whores hold sway over several important characters and play a pretty significant role in the book (Tyrion spends all of ADwD trying to find out where it is "that whores go"). Slavery, though, is the biggest moral taboo in Westeros, not prostitution.