Well, for one it is a serious code violation and has been for MANY years.
Having the hot side hot all the time is only half the issue. With the neutral switched the neutral is also hot as it is being backfed through the load to the switch. So anyone working on the circuit (like him I bet) without shutting it off completely could be in for a (possibly deadly) surprise.
If he is this insistent on doing something so stupid and wrong I would be suspect what other violations he is adamant about creating.