Most of the community, after looking at the pictures, has concluded that the underage thing is either stupid (nobody look like a kid) or ambiguous enough that it's stupid to say it's underage anyway, so the theory is that the users were banned not so much for the underage as for it being two males doing the porning.
I think they have at least a bit of a point, considering that Hermione/Snape is an equally big pairing and stuff for that is also frequently underage, yet it seems to be a nonissue as far as what LJ abuse is actually throwing off the site.