JT never said that those practices are acceptable. His objection was to the term "barbaric". He said he would prefer "absolutely unacceptable", or another such term. I don't see how that makes him a weak cultural relativist.

Webster's dictionary: Barbaric = 1a: of, relating to, or characteristic of barbarians; Barbarian = 1: of or relating to a land, culture or people alien and usually believed to be inferior to one's own.

The word has other meanings too, but you don't want to use ambiguous words in a citizenship guide.