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.