"As has been said, 2500 posts ago and probably yesterday, to believe that Mary remained a virgin is not the same thing (and indeed light years away) from the heresy that purports Mary to be "sinless."
Well, yes those two things would not necessarily be co-extensive. Why do you think that the doctrine of the sinlessness of Mary is a heresy? Is it because you reject the Latin dogma of the Immaculate Conception or because, like, for example, +John Chrysostomos, you believed she indeed did sin after her birth or both?
"...The only grounds the Roman Catholic faithful have for believing in the teaching of the assumption is that a supposedly ‘infallible’ Church declares it. But given the above facts the claim of infallibility is shown to be completely groundless. How can a Church which is supposedly infallible promote teachings which the early Church condemned as heretical? Whereas an early papal decree anathematized those who believed the teaching of an apocryphal Gospel, now papal decrees condemn those who disbelieve it. The conclusion has to be that teachings such as Mary’s assumption are the teachings and traditions of men, not the revelation of God."