In the context of the article...
The same way bars police unruly drunks. Bouncers.
As a long time doorman at a private membership only liquor bar in Texas you have no immunity from prosecution if you physically touch aka assault someone if crap breaks out and your customer is injured or harmed in any way at all. I know from first hand experience.
As a bouncer you hope it doesn't come down to charges being filed for assault against you if you go too far but you can be filed on and arrested for assault if the situation goes sideways on you. It usually didn't though thankfully. Seen it happen a few times over the years with the inexperienced young and tough breed. Kind of depends what is considered to be what is reasonable enough force to use. Was never arrested but was advised by dispatched officers to be careful.