Regardless of who's telling the truth in the he-said, he-said debate, I hold the official responsible. Someone on the court has to be the grownup, and that's always the officials.
I'd agree, partially. Yes, the official should retain his/her poise and always remain the adult, but once a coach lays hands on or physically threatens an official, being "the grownup" does not include accepting the first blow.
If it does come to blows, win, lose or draw, every official OWES it to every other official, to file, and follow through with, the maximum charges against the aggressor coach.