I don’t know why I should bother at this late date, but here goes.
The notion that one’s religion, nationality, ethnicity, genealogy, and mother language are all separate things that have no necessary relation to each other is a very modern concept.
Judaism is a very old religion/nationality/ethnicity, so old that our modern ideas about the relation between these concepts don’t apply.
Think more about tribal identity. Like, say, Apache. Apaches had their own religion, their own language, their own territory, their own ethnicity. You could become an Apache if you were adopted into the tribe, but you couldn’t just decide to believe in the Apache religion and have other Apaches consider you an Apache. They’d have to agree to include you, and they would only do that for reasons that seemed good to them.
And likewise, you could be kicked out of the tribe if you made yourself unpopular enough, but whether you were an Apache or not an Apache was decided by the Apaches, not by anyone else. Maybe if you converted to Christianity, they’d kick you out. Or maybe they wouldn’t care. But just because Christians could consider you both an Apache and a Christian, that doesn’t mean Apaches necessarily would.
This premodern conflation of religion and ethnicity is actually pretty common around the world. For instance, go to a Hindu temple and tell them you want to convert to Hinduism, and they’ll look at you like you have two heads, and not in a good way. Because for most Hindus, Hinduism is simply their traditional family/ethnic practice, and since you’re not joining their family or ethnic group or community, converting to the religion is nonsensical. However, a kid born to Hindu parents who grows up in America, speaks only English, and never goes to temple is still a member of their group in their eyes, unless they take affirmative steps to outrage the group.
To put it in yet another way, you can be Italian and Catholic and a citizen of the United States and speak only English. If you join the Baptist church, you’re still Italian. You can’t become Italian by joining the Catholic church and leaning Italian and hanging out at Italian Restaurants. You could even become an Italian Citizen, but that wouldn’t make you ethnically Italian. In fact, there’s really no such thing as Italian ethnicity when you get down to it, because a Sicilian and a Venetian might live in the same country, but they don’t consider themselves as having the same ethnicity, and won’t understand each other’s vernacular, although they probably both understand “standard” Italian.
