It's a gnostic interpretation of 1 Corinth ins 1. Someone could just as well apply it to any professional, not just the office of civil minister. JL is miles away from orthodoxy and both the Westminster and London Baptist confessional standards.
His reasons for leaving Reformed theology aren't rooted in Scripture. That's my biggest problem. He should appeal to the Word of God, not his own morality about hell.
The reformed churches used to apply the regulative principle of worship (Google it). Instruments in worship were seen as a vestige of animal sacrifice. I'm not confident with either side of this argument but a lot of churches go overboard with the praise team, even playing mood music to improve both prayer and the sacraments.....