What's culturally jewish?
He seems pretty upset everytime some is like "just how jewish are you?"
Asking Europeans a question like this. 

Fair. Being French probably account on some level to how tortured a phrasing that was.
It's not a great label, that's why I put it in quotation marks. It covers a variety of situations of people that come from Jewish parents, family, lineage or background but live a secular life and/or are not recognized
officially by whatever arbitrary standard their religious denomination uses.
Basically what I wanted to say is that Sanders is a secular Jewish person.