Full Idea
MacIntyre formulates relativism in terms of rationality rather than truth or objectivity. Things are rational relative to some particular tradition, but not rational as such.
Gist of Idea
Relativism can be seen as about the rationality of different cultural traditions
Source
report of Alasdair MacIntyre (Whose Justice? Which Rationality? [1988], p.352) by Martin Kusch - Knowledge by Agreement Ch.19
Book Reference
Kusch,Martin: 'Knowledge by Agreement' [OUP 2004], p.273
A Reaction
Personally I had always taken it to be about truth, and I expect any account of rationality to be founded on a notion of truth. There can clearly be cultural traditions of evidence, and possibly even of logic (though I doubt it).