another day, another ben masada picking-a-fight-with-christians thread. *sigh*.
in fact, i believe mary was supposed to be a benjaminite, not a judahite - politically this would have solved quite a few problems by unifying the royal succession and removing opposition relating to surviving claimants of hasmonean or kishite (ie from king saul) descent.
a child of rape by a roman soldier wouldn't be a mamzer; some incestuous component would also be needed.
claims that jesus was the son of G!D of course would be taken with somewhat more than a pinch of salt, however.
I don't find anything in the gospels that tells me of Mary being from the Tribe of Benjamin. The closest reference to Tribal genealogy as Mary was concerned is in Luke 1:5,36, that Mary was of a relative of Elizabeth descendant of Aaron the Levite.
And with regards to being a mamzer, if there was anything which would morally prevent a man and a woman to get married to each other, a child born of such a couple would be a mamzer. Mary could never marry a Roman soldier if she was already married to Joseph. Therefore, IF the rape ever occurred, Jesus was a mamzer. But of course, it never occurred. The Christian claim that Jesus was not a biological son of Joseph's is only an attempt to keep the idea that he was born of God with Mary.