I don’t understand why people make this distinction.
A Jew can be a christian.
But what is a Jew?
Most people seem to think of Rabbinic Judaism (which is younger than christianity).
But weren’t Mary, Paul, James the Just, Simon Peter, Andrew, John the Baptist, Mary etc. all Jews.
Now I’ll even play Devil’s advocate.
What if Jesus wasn’t the messiah but the messiah has yet to come.
What if a young Jewish lad from Romaniote Jewish background called Rae Frizis turns out to be the real Jewish messiah. A lot of Jews accept him, a lot of Jews don’t. After some time the Jewish believers call him Rae the Promised One. During Rae the Promised One’s life they are open for conversion for non-Jews as his teaching are for everyone. After some time someone calls some followers of the Promised One, Promistian to crack a joke at it. Within months, everyone calles them the Promistians. The Jewish persons who didn’t accept Rae Frizis would claim that the Jews who followed Rae Frizis aren’t Jewish, as the Jewish messiah has yet to come.
Those followers of Rae Frizis would still be Jewish. I really don’t know why we should use the definition of the Jewish who refused the Promised One.
Messianic Judaism is a form of Judaism, but it is also a form of christianity. The one doesn’t exclude the other.
But it certainly isn’t the same like most other forms of Rabbinic Judaism.
If you look at Judaism as Rabbinic non-messianic Judaism than I understand why you won’t see them as Jews. But I’m not inclined to argee.
What I do find weird is that lot of christians seem to side with you, given that they believe Jesus was the messiah.