I was not the one that made the claim that knowing about Mary’s perpetual virginity was vital to salvation. That was your “reformers,” and some of the ECFs. I pointed out that knowing things about the Kingdom, about the people and heroes within it, and about how God chose to do things, are helpful to our understanding and deepen our connection in love with Him and all His Kingdom. They may not be absolutely necessary, but they are helpful. And so it is with Mary’s perpetual virginity.
I think that many who strove to defend the honor of Mary against her assailants did not believe that such beliefs were essential to salvation, but since they WERE truth, and related to our adoptive spiritual Mother, to deny these things, to speak against them, was a terrible thing. It was rejecting truth and slandering God and His handmaiden.