First off, it seems like the primary people Jesus was mean to in the gospels were religious people.  The religious people were well-intentioned, thoroughly Biblical and convinced they knew the truth.  Off the top of my head (which is a rather dangerous caveat), I can't think of any "outsiders" Jesus was particularly mean to.  Jesus was consistently mean to the Pharisees -- not the Romans, Gentiles, and irreligious Jews.  So when we talk about being mean, it seems to me that we are called to be mean to the people Jesus was mean to -- religious people, people who believe they are on the inside.  That's us, the church-going types.  Jesus would be meanest with us -- not those on the outside. 

Honestly, I see a tremendous shift going on within the church as we wrestle with the reality of Christ's approach.  I see people who are giving up being mean to those outside the church (it's a little strange we would demand Christ-like behavior from people who don't have the Holy Spirit in them) and are turning their critcal gaze inward.  For me personally, I feel so incompetent in my followership of Jesus that it seems hypocritical to point the finger at people "out there" and demand right behavior from them.  There's plenty of wrong behavior, wrong attitudes, wrong heartedness (is that a word?) in me to warrant the meanness of Jesus.