Are you calling me a liar now? Would you like to produce some evidence that I have at any point stated a Jew ceases to be a Jew if they become a Christian?
No and No.
I read it. This is not rocket science, Jerusha. Christianity does not teach what you are claiming it teaches. I've actually not met another Messianic that insists that it does.
No, it's not rocket science. It's just plain Scripture as found in Romans 11 and that alone is reason aplenty for Christians, including Messianic Jews, to believe it.
As to your not having met any Messianics who believe this, all I can say is that you need to get out more. Just a few examples:
A quote from Messianic, Sam Nadler: "If you’re a Gentile you too have been grafted in among them, not to replace Jews, but among the Jewish people, to make them jealous (Romans 11:11)"
Messianic, Ellen Kavanaugh states of Romans 11:17-27: "Sha'ul is explaining here that because of mainstream Israel's rejection of Messiah, non-Israelites (wild olive branches) who accept Yeshua have been given a place in Israel's cultivated olive tree. But note these wild olive branches remain wild. Gentiles do not become Israelites here, they merely share the tree with believing Israel. Gentiles are further warned not to boast about G-d placing them in the tree, because they too can be removed. In fact, G-d reminds them that the natural branches would graft back in well since its their own tree and their own nature to be included in it; but it is contrary to the very nature of the wild branches that they too are included! So yes, Gentiles can be placed in the tree of Israel, but at no point do they become cultivated -- they always remain wild branches grafted into a tree not their own. When a Gentile becomes a part of Israel, they still remain a Gentile (albeit a Gentile counted among Israelites). Now note: The One grafting these wild branches in is G-d, not man."
Since you're in the Cinci area, stop in and have a chat with Rabbi Mike Wolf at Beth Messiah for he states "Gentiles who place their faith in Yeshua, are “grafted into” the Jewish olive tree of faith."
And a whole lot more including my congregation:
http://www.man-na.com/Statement of Faith.htm
Does that mean you are going to quit labeling yourself a Messianic Jew?
Uh...Nope! The question when signing on here is what is your religious affiliation. My religious affiliation is Messianic Judaism. Since Messianic Jew is all that is offered for that, that is what I chose. Perhaps you should petition Knight to revise the offerings.