Sounds like Peter got the thumb screwed down on him just because of a letter his father wrote to Rutherford.
In turn he got inadvertently shunned by the rest of his close and fellow JWS because of his father's letter,
so he was more or less pushed into writing a letter of disapproval concerning his father's deeds.
Putting situations like this together with all the opposing animosity from outside the organization,
its no wonder why the WTS. came up with such strong armed DF practices.
From the time when Rutherford first grasp control over the WTS. he was probably in a constant
state of paranoid nervousness of whether or not he could maintain this sought after personal
kingdom of power and control.
Any sign of diversion or dissonance among his surrounding peers and they were quickly chopped
at the heels and cast away.
As with all man made power structures such as this, the holder of the upper most power, thwarts dissension by acts of discipline
to keep certain ones separate and away from the rest and as a means to show what can happen to those who pose hindering questions
onto the activities of the person holding that position of power.