I don't know Micheál Ó Fearghail nor have contact details for him but regarding his comment
The SSPX priest followed Canon Law in giving a Requiem Mass 'without prejudice' to someone who apparently was a practising Catholic. They knew there would likely be a media fuss about it, and there was.
Why cast the doubt? Erich Priebke was a practising Catholic. That is a fact.
I am sorry I never got to meet Priebke. I would have regarded it as an honour.