It takes many forms:
The Blue Wall of Silence
We must protect the church
We clean up our own messes
You will weaken the Presidency/administration in a time of war/crisis/national emergency
An outsider cannot understand
You will take away the motivation to take risks
... and you can offer your own version . . .
It is the excuse not to public identify wrongdoers or to be subject to outside oversight or to allow criminal investigation and prosecution
The claim is that to do so will weaken the Police Force / Church / Military / Business / Organization
The claim is wrong. And failure to fully investigate and expose weakens the institution, because it inevitably leads to an arrogance and the same or similar behavior continues, or happens again. . . and again . . . and again. . .