He's not wrong. The AP is only recommended for RNAV departures. I have flown the ATL RNAV departures many many times using the FD but not the AP. I have seen many CAs do the same thing.
Many of the deviations I have heard about come from either not setting the departure up in the FMS correctly or having the HDG bud not on runway heading when the AP is turned on.
If you dont load the right runway into the box then the airplane will not fly the departure. It wouldn't matter if the AP was on or not. If you have the heading bug on the wrong heading the FD will command a turn when you shouldn't be doing one.