This is an unusual story. Particularly so, if plugged into our contemporary religious society. Try to imagine if you can, someone as holy as Jesus--calling someone as unholy as Levi to be part of his ministry team. Levi was a Jewish tax collector, so in his day he was considered a traitor of sort. Think about it. What could alienate you more than becoming extremely wealthy by extorting exorbitant taxes from your own people group for an oppressive government? What's more, the fraternity of Levis' business associates was a collection of more of the same!
Jesus' calling changed the trajectory of Levis' life, but in the process Messiah befriended the unfriended brotherhood of thieves that were Levis' peers. That being said, I think it is safe to assume this--if God became flesh today, rather than two thousand years ago, his FaceBook friend list, pictures, and status updates would include some of today's most colorful and disreputable "sinners."
Question? Would we be asking "Why does Jesus associate with such scum?" To go one step further--would we hold in contempt other Believers who friended the unfriended? Would we unfriend Jesus?
According to Jesus, the question posed by the Pharisees revealed more about the interrogators than the transgressors. Interesting, is it not? Jesus words to those who think they are too righteous to be among those who know they are sinners were pretty scathing.