That's the million buck question, isn't it. You don't know what you don't know, until you finally know. Hopefully not the hard way.Just curious, how are CCR students, who are new to CCR, establish that their factory certified instructor is "demonstrably untrustworthy"?
A reasonable Google search of the name, once you get up to the higher echelons of "named" instructors, should hopefully give you some ideas. A search for Peter Sotis on Scuba Board would raise some eyebrows for sure.
Sadly, most students never know if their instructor is doing the right thing by them until long after when someone else spots the deficiencies and (hopefully) says something.
I believe the majority of CCR instructors are doing a pretty decent job, and aren't very likely to get you hurt on a course. If you want to make sure, a thread asking for comments and recommendations on the appropriate forum here should help. Any truly egregious issues find a way to surface here, diving is a much smaller world than most think.
Also, any reasonable instructor would have no problem giving you a way to get references from their last few students as well.