Of course the rule still applies, was it appropriate response? “if nobody sees it, it’s the bouncer’s word against the drunk’s”.
I have seen bouncers lose it on a guest. Three of them hauling the guy out after he spilled drinks on a girl from the upper level, then when her friend (also female but 6’3" athletic and stacked) confronted him he started a shoving match. As the bouncers were actually carrying him out, he tried to punch one of them. The guy got a few retaliatory punches in before they ended up with one bouncer shoving the guy out the door, the other trying to restrain the third bouncer (275lb, whose daytime job was heavy diesel mechanic). Drunks don’t always make the best choices, but they excel at causing trouble. Bouncers are rarely chosen for their even temperament and wiliness to ignore insults and attacks.
In Canada, IIRC, a citizen can lay a complaint and even pursue the charge, but the crown attorney (prosecutor) has the discretion to withdraw the charge if they don’t feel it’s in the interest of the court to continue.
Bouncers that exceed reasonable force will likely sooner or later go too far; they, either cause so much injury the police cannot ignore it, or the imbalance in strength was too obvious, or in these days, someone catches the beat-down on a cellphone. It’s a bad idea for the bad idea for the bar to ignore or condone this, since they are the one party with deep pockets that can also be sued.