Good ol' fashion Witch Trials.
Have one of the higher ups in the church going round random towns and villages putting people on trial for suspicion of using magic. Have them publicly torture a 'confession' from them and those close to them. Then have the poor victoms executed in a horrible way, no matter their age/gender/physical or mental state (before the torture).
That should drive the good aligned characters in the group to start really hating the church. Even the neutral characters should start feeling that this isn't right. The evil aligned characters (if any) will start to either get jealous of, or be spurred on to out do them.