In every state I've done the research in, assault is the 'threat' part, so a continued honking like that could easily be considered assault. There was a case in TX where a driver was charged for exactly this kind of threatening behavior.
One of the best things one can do to actually be a safety advocate, if you can, is get video of this kind of incident. Hell, just pointing your camera at an aggressive driver will often de-escalate the situation as they realize the trouble they can get in (and yes, I've done this many times, so far with 100% effectiveness).