My wife's at an advanced stage of ADI training - with a local independent, not one of the big 'schools'.
There seems to be nothing in the syllabus, test, or materials typically used by PDIs (a pre-qualification ADI) which adds anything to a typical driver's knowledge about cyclists. A driver who thinks two feet is plenty of room won't have any reason to change that view unless a) their instructor makes the effort to teach correct passing of cyclists or b) they fail their Part 2 because of a poor pass. (Question: how much do driving examiners know about cycling?)
I don't believe the driving standards required of an ADI are particularly advanced, and the hardest test to pass is Part 3 which is all about teaching technique. Obviously most ADIs take pride in their profession and work hard to achieve a high rating. Unfortunately instructors with RED are likely to be fairly inexperienced and may be only partially qualified (I can't be sure whether RED uses PDIs for teaching).
An ADI is assessed on a 6-level scale, with 1-3 being a fail, and 4-6 being progressively higher ratings. They need a 4 to initially become an ADI, and are subject to 'check tests' regularly, at which their rating can be changed (not sure what happens if they fall below the minimum standard though).
If you complain to the Driving Standards Agency there's a possibility it might trigger a check test, but I don't think they can directly reprimand an ADI.