Messianic Jews: not Christians?

Messianic Judaism, Gentile Church, and Supersessionism

It is common in the Messianic Jewish community to not call themselves...or even claim that they are..."Christian," even though they believe wholeheartedly in Jesus as Messiah and Lord. Often, the reason presented is that to many Jews, "Gentile" connotes "Gentile" (or is  Greek term, when the Hebrew is preferred).  

Consider this, though, from Michael Bird's post, Messianic Judaism, Gentile Church, and Supersessionism:

However, one thing that causes me angst is the premise that while Messianic Jews and Gentile Christians are part of the one ekklesia, still, there is assumption that they inhabit different socio-religious spaces, and Messianic Jews are not actually “Christians.”  The impression I get is that Messianic Judaism is presenting itself not simply as an ethnic church group or as a Christian denomination, it is touted as a separate species of Christ-believer, one more entrenched in its Jewish heritage and distinguishable from the Gentile Christians. To be honest – and Joel might push back on this – I think Galatians rules out precisely this kind of vision of believers in Jesus. First, when Paul says that in Christ there is “neither Jew nor Gentile,” he is creating a shared meta-identity where it is union with Christ that is determinative for our relationship with God and to each other, with the result that all walls between these groups are utterly broken down. What is more, Paul particularly wants to avoid any kind of ecclesiology that results in someone insisting on foreskins sit on the left and no-foreskins sit on the right. I think Paul knew of both mixed and parallel groups of Jewish/Gentile Christ-believers, but not two species of believers.  Second, despite the aversion to using the word “Christian,” I cannot help but note that Christianoi was originally used for mixed Jewish and Gentile groups in both Antioch (Acts 11:21) and in Asia Minor (1 Pet 5:13). Christianoi means “client or adherent of Christ.”

Note: the excerpt above is from a review of  Introduction to Messianic Judaism ,a collection of essays from Jewish and Gentile writers (including genius gentile Craig Keener) See Scot McKnight's review of the book here  #1, #2)