If my car crashes or I am extorted due to my sexuality or killed for my religion. All the same. It is deadly. Data Privacy is not a nebulous concept. It is a human right.
If you have to keep your religion secret to avoid being killed, you have MUCH bigger problems in your society that I don't think "nobody knowing who is secretly Jewish" is actually going to fix.
It's not like a future hypothetical fascist dictatorship isn't going to have access to the necessary records to piece it together or would follow its own GDPR constraints, nor would the GDPR stop it from arbitrarily deciding some people are Jewish without detailed evidence.
I'd like to think the GDPR is underpinned by better philosophy than a false hope it could prevent a future Holocaust.
I think it is generally based against discrimination and not focused on something extreme as a state organized Holocaust. Also GDPR does not care about this. For the GDPR these are just attributes which should be protected.
A core rule of data privacy is to restrict yourself to the necessary information you need. Religion like sexual orientation is rarely justifiable why it is collected at all.
It's not like a future hypothetical fascist dictatorship isn't going to have access to the necessary records to piece it together or would follow its own GDPR constraints, nor would the GDPR stop it from arbitrarily deciding some people are Jewish without detailed evidence.
I'd like to think the GDPR is underpinned by better philosophy than a false hope it could prevent a future Holocaust.