He wants to superimpose his system upon the grace believer. He loves to meddle in the affairs of other believers. He tries to run their lives. He sets himself as the criterion of spirituality. It is open season on Christians.
People love to pass judgment on believers.
It is also a favorite indoor sport of Christians. Christians love to judge other Christians. First remove the plank from your own eye, and then you will see clearly to remove the speck from your brother's eye. The Christian is to not let legalism judge him. If we are in the habit of passing judgment on other Christians, we will find ourselves the victims one day.