The song is more about the christians that are judgemental to a fault. Some christians seem to take delight in looking down at the "sinners" around them as if following what extra standards they have added to God's Word and his natural law somehow makes them better than everyone else.
The song is trying to point out (and very harshly) that these judgemental christians need to realize that they themselves are sinners that will be judged along with the rest of us standard disregarding sinners.