You get into the trickiness of being Jewish. We are both a people and a religion. And accepting Jesus makes you a Christian. And in many less Jewish than an atheist Jew. because the later is not actively practicing a religion that is contrary to Judaism.They are now. But they were born Jews. I do not try to convert my Jewish friends and colleagues to Christianity. But it does happen now and then. They don't stop being Jewish just because they are also Christian any more than a non-believing Jew is not Jewish.