Straight off - an apology: sorry if you think this song is a bit, well, unfair to Paul. Let me explain. We get hints in the New Testament that Paul may have looked somewhat unimpressive in person - 1 Corinthians 2:3f, 2 Corinthians 10:10 - and there's an apocryphal account which describes Paul as "a man of little stature..." (see the New Bible Dictionary article on Paul).
However - and it's a big HOWEVER - the message that Paul had: WOW! That was amazing.
So that's the angle this song takes - Paul himself, maybe not that cool, but WOW! the things that he said!