Obama's Christianity

A reader makes a good point:

I thought that one of the few things all us Christians agreed on was the maxim "condemn the sin but love the sinner."  Obama's description of his relationship to Rev. Wright, the man and his opinions, was a model of this goal for all Christians living in a tainted world.  So how can Christians such as Michael Gerson (whom I otherwise respect) continue to demand Obama sever himself from Wright and Trinity Church?  What am I missing?