I can tell you my opinion on why it's hard for a lot of people to separate them. Jews refuse to separate themselves, by and large, from their own extremists.

If a crazy Christian does something, and it is pointed out that he was Christian, other Christians will say- Hey that guy was an extremist, we don't associate with that.

If a Talmudic Jew does something terrible, other Jews will, rather than call out this individuals extremism, cry anti-Semitism. Which makes them appear to be defending them.