I agree with Popa’s interpretation of the letter.
I also think that promulgating such a letter is probably not the most tactful way to achieve peace.
But I do not think the letter writers were out of their bounds. There is no such thing as someone to choshuv to criticize. The nevi’im knew that and Chazal knew that. ????? ????? ??? ??? ?????? ???? ???. We are not idol worshippers. If they know R’ Stav to be what they say he is, their words are right on target.