That isn't what Luther wrote. As per Jaroslav Pelikan (who is not a member of the CARM forums due to being a lot smarter than all of us here and also being dead), the Latin text of the Smalcald Articles is a translation of the original German text. The original German text did not
contain the notion of "Mary, pure, holy, and ever-Virgin" (ex Maria pura, sancta, Semper Virgine
.) See his comments in his book, Mary Through the Centuries
(New Haven: Yale University Press, 1996), 158-159.
Some years back I interacted with one of Rome's defenders, who, in essence thought the German versions of the Smalcald Articles were engaging in a Marian cover-up
. Here we see that the actual historical distortion is attributing the Latin text to Luther's German. The question though is why did the Latin text use "ex Maria pura, sancta, Semper Virgine"?
Why was the Latin was translated “Mary, pure, holy, and Ever-Virgin”? Perhaps the the translator used the phrase as a force of habit (as it was a common phrase). Perhaps the translator believed in Mary’s perpetual virginity and Immaculate Conception. It could also be that the Smalcald princes thought the phrase would gain more in a hearing with the Papacy? It’s also possible that the sense of “pure” was only to indicate that Mary was a “real creature or truly human
” [See: Heiko Oberman, The Impact of the Reformation
(Michigan: WB Eerdmans Publishing Company, 1994) 241.] which was a sense in which this word was used in the 16th century.
Details of the Latin translation / translator can be found here
(see the discussion starting on page 332). The Latin translator "fell into disrepute
" as per "evinced Roman Catholic leanings
And now you know... the rest of the story!
Edited to add
: The thrust of my comments is not to deny Luther's adherence to Mary's perpetual virginity. The above should be read with the emphasis on the notion of the immaculate conception: a Roman deviation which Luther did ascribe to early in his career, but later rejected.