In this interview on the Philosophy Bites podcast, Boghossian talks about moral relativism, giving some shades of the view: e.g. you could be a relativist about manners but not really about the underlying principles girding them (“be polite!”). This accords with Smith’s version, in which the most important moral points–e.g. generosity is good–are going to be universal, but lots of cultural factors are going to go into when and how much generosity is considered appropriate in a given circumstance.
Read Wes’s post from August on the Boghossian/Stanley Fish exchange that the Philosophy Bites page refers to.