That is something to keep in mind in regards to McLaren nowadays. Maybe it wasn't as strong in something like "A Different Kind of Christian", which I wrote a bit about a few months ago, but it's showing up now and stronger. The association with people like Jim Wallis and Sojourers has seemed to encourage him to voice political views.
Luke is very interested in the ways that disadvantaged people of his day--the poor, the sick, the women--respond to God...
This is echoed a few pages later, regarding the story in Luke of the shepherd's visit to the child Jesus.
Remember what we said about Luke's fascination with disadvantaged people? Here we have it again...They (the shepherds) had little to no status in the world. They were the humble and the poor whom God was now raising up to receive heavenly messages and an audience with the great King...
Is this a 'for certain' thing?
First off, was this something new God was doing, something He hadn't done before? How about Joseph--slave, prisoner, made second in command of a powerful nation. How about Moses--very topsy-turvy in this regard, child of slaves made child of royalty who became an exile and a shepherd who met God and became a leader and an instrument of deliverance for his people. How about Gideon--a little guy who was out doing his job in very adverse condition when God called him to go to war. How about David--little kid keeping sheep becomes a war hero and after some tumulous times of running becomes a king and a poet and a prophet. And there're people like Elijah, of whose background little is known.
Of course, one could just as easily point out examples of people in other social spheres who were used by God--Abraham, Job, Daniel, Solomon. I've read where Isaiah may have been of pretty high family, though I'm not certain of that.
And there is one more thing about Jesus--the fact that for all that the humbleness surrounding His birth, He still came of Israel's kingly line, going back to David. His geneology is given twice in the Gospels, so one would think that it must be pretty important.
Does Luke care about the social status of those he is writing about? Maybe. But maybe not, too. It is something being read into the story, perhaps with reason, or perhaps not. At the least, making Luke into some kind of polemic about the disadvantaged and the lowly is questionable, and seems more like the writer's attempts to insert his politics then any kind of biblical thinking.
My purpose here is not to say that God does not use those of low social status, and doesn't care about them. My purpose is to say that God does not exclusively use such people, but has used people of all kinds of social classes and statuses. The Christmas story does have shepherds of little wealth and status, but it also has wise men who do bring rich offerings for the Christ child.