"Also, I believe Ben Witherington argues for a Jewish Christian (again, hist term) audience for 1 Peter in his commentary Letters and Homilies for Hellenized Christians. If I recall correctly, Witherington thought this bolstered his case for authentic Petrine authorship."
"For you know that it was not with perishable things such as silver or gold that you were redeemed from the empty way of life handed down to you from your ancestors" (1 Peter 1:18)
"But what about the statement about being 'ransomed from the futile ways of your ancestors'? This, to be sure, could be a reference to the audience having a Gentile background" (pg. 31of Letters and Homilies for Hellenized Christians by Ben Witherington III)
"Thus the question becomes whether our author [Peter] has something of a...supersessionist reading of the earlier history of Israel or not...I do not think that such a [supersessionist] view can be lightly dismissed....Whether we call this completionist or supersessionist rhetoric, clearly enough our author [Peter] feels that he can make such a hermeneutical leap..." (ibid) [emphasis added].
Peter: I'd like for you to answer my question: is keeping enough Judaism--enough Jewish lifestyle--so that subsequent generations consider themselves Jewish, is that what Peter meant by "empty way of life"?
Gene: I know of plenty of secular Jews today who have inherited from their parents an "empty way of life", one that had little to do with whatever little Judaism they were exposed to and one that had little use for G-d. Yet, they are still Jews and for those of them who cared about being Jewish enough to in-marry, so are their children. It's not that hard to imagine the same being true in the first century.
Peter: Saying that Jewish identity has little to do with Judaism is like saying sunlight has little to do with the sun.