Yo BE CAREFUL with things like this because Nazis can easily weaponize the court system against you.
This is not legal advice and this is me, just talking about some jurisdiction-specific things I happen to know, as a defense attorney who's done so many A+B cases...
Assault and battery are different things. Battery is actually making contact with a person (i.e., the root of the word "battered.")
Assault can be done one of a two ways in common law.
Attempt battery and miss (throw a punch and whiff it)
Make someone think you're about to do battery even if you don't intend to
That second one can be tricky!! Generally, words are not enough for an assault. There must be some type of accompanying behavior, such as violent gestures (balling up fist, advancing, raising an item threateningly). Whether or not your words are a threat is also relevant; we have some great case law in this state that a threat involves a direct threat, not a conditional statement.
(That means you're on safer ground if you say "I will beat the shit out of you if you continue to display your heinous Nazi sign" than if you say "I will beat the shit out of you in five seconds.")
I see in this video that this guy balled up his fist and pointed in some gestures to "get the fuck out of here." I would likely not recommend that anyone do that. I would also not recommend "The only good Nazi is a dead Nazi" because, while true, it could be construed as a threat and therefore part of the relevant behavior to reach an assault charge. (Probably ok in this instance because this guy's sign said "the nazis were right" not "I'm a nazi." This seems trivial but could be an important distinction.)
Mind that my analysis is particular to my jurisdiction and there are many variants of this law. It is actually extremely difficult as a layperson to get a good picture of this in my jurisdiction specifically because the law forbids "assault & battery" without defining it, and the definition can only be found in the common law.
Be safe and don't give anyone reason to call the cops <3