You think that it is ok for 3 rabbis who are elected to run the RCA to say things like that about one of the gedolei hador? This is insane. Insane.
I would 100% agree with you if Rav Yosef heard first hand from Rabbi Stav. However, from the Statement of Rav Yosef, he “accepted Eidus” regarding Rav Stav. We have recently seen (specificly with Rabbi Lipman & Rav Feldman, but others as well) how “eidus” is in many cases not true in the end.
Now, I agree that it doesn’t justify the language used by the RCA, but it seems that such language is the norm when involving any disagreement in EY (unfortunately).
Call it a “Limud Zechus”.