Martin was more interested in arguing against the Church hierarchy's existing relationship with the people, rather than fencing about what angels could, or would, or whatever.
I agree there is a problem with the word "literal." I think it is misleading to speak of a "literal" interpretation of the Bible. At least in an American context, "literal" to most people means either dispensationalism or Fundamentalist legalism (or typically, it means both at the same time). Lutheranism takes the Bible more seriously than so-called literalists who often read esoteric theories and timelines into the Bible. This is also different from the liberals who interpret the Bible (in so far as they regard the Bible at all) according to the latest fads.