It's not just open or hidden retaliation that dissuades residents from complaining to the ACGME about stuff like this, or work hour violations, or anything else.
It's the realization that action taken against their program can impact their ability to finish residency on time and get a job on time and move on with their lives. Nobody wants to graduate from a program on probation, or have to find a new program mid-residency if the program gets shut down, or rely on references from faculty or a program director who get slapped by ACGME. If indeed a slap actually happens.
There are a million ways to retaliate against residents, openly, subtly, and silently just with weaker or less enthusiastic recs for fellowship or jobs.
We all know this to be true. It's not unreasonable for residents in these situations keep their heads down and grind out the residency and move on with their lives.