I'm not the person who originally posed The adventures of Nazi Norman and Bob the Jew, so if you'll indulge me in a slight correction to the source material: "Bob the Jew must die", depending on context^[1], may very well be a pointed threat, but to eliminate all confusion, let's kick it up a step and let Nazi Norman say: "I'm going to kill Bob the Jew". This would clearly be outside the protection of free speech in the US system.

To say "I'm going to kill Bob the Jew" is a threat that shows immediate and pointed intent to perform a particular murderous act. In short, shit is going down, it's going down right now, and this isn't so much a statement of opinion as it is just a bugle call before I go rushing in. A reasonable person would assume: The speaker has chosen the victim. The speaker has broadcast intent to act. The speaker is capable of acting. Shit is going down.

While "All Jews must die", if enacted, would involve the death of our good friend Bob, it's not nearly pointed enough to stand out as a broadcast of impending act. It's dubious whether it's an intent or just a (perhaps impotent) wish. There is no indication that the speaker knows of Bob's existence. Even if we're to assume intent, there's no indication that the speaker is intending to spark up a genocide right now, both through lack of clearly saying so, and because Nazi Norm over there is hardly capable of mustering up a genocide on his own. If you told the police "Nazi Norm says all Jews must die", they'd still have to dig through questions from "What do you mean 'must'?" to "How's he going to kill all Jews?" before rushing off to protect someone.

And that line between broadcasting intent and broadcasting preferences, as close as it cuts, is the line that separates protected speech from unprotected. You can wish, want, and advocate for whatever you like, but until it's immediately, obviously, and inevitably on the path to action, it's not comparable to action and not considerable as such.

^{[1] Depending on context, it could mean anything from "Bob the Jew is mortal, and like all men, he must [eventually] die", to "Right-thinking people should want to put an end to people like Bob the Jew", to straight up "Here's the rope, there's the house, back in five". It's a less-than-perfect analogy. Allow me to disambiguate.}