Having worked in the security industry, both as a patrol officer, and a dog handler, I wouldn't advise anyone to try and push things too far with an aggressive person, it's bound to end badly, and it's really not worth it! Your employer expects you to do a job, fair enough, but they by and large are not going to be too bothered if you get hurt, and god forbid you should lose your life, I'll guarantee you'll be forgotten in a few weeks. I've dealt with some seriously aggressive people in my time, and in some cases I've let them walk away, in others they've been nicked,it all depended on the situation. My career ended after an armed robbery, I was dealing with one site while at the same time there was an armed incident taking place at another. The criminals stole a truck full of scrap metal, rather than the truck containing the high value electrical items. It was widely believed that due to the severity of the incident (2 guards threatened with guns, beaten and tied up) that they'd return when they realised their mistake. The police advised that security be increased, including bringing in a dog handler, as they were unable, understandably, to maintain a presence at the scene for the next few days.
My employers solution was simple, he informed me that to avoid compromising security at the other site, and possibly losing the contract, that I was to leave my two GP dogs on site (free running), and attend the other site myself, with no dogs!
When I pointed out that not only was it pointless sending a dog handler with no dog, plus it was actually illegal to leave guard dogs free running on a site that had no handler present, I was told to shut up and get on with it! Needless to say I refused, and quit the job.
At the end of the day, saving a firm a few quid for a ticket is not worth it if it risks someone losing their life, plus if it does get physical, you're usually the one who gets the grief off the public, seen it too many times with the police. You end up with 3 of 4 officers trying to detain a suspect, then a member of the public starts whinging about why it takes so many of them. It's simple really, whilst a criminal can use whatever violence they see fit to escape custody, the law prevents someone acting lawfully to detain them from doing the same,they can punch you in the face to get away, but you punch them in the face to stop them fighting, and all hell brakes loose, it's a one sided thing, and at the moment it all seems to be stacked in the criminals favour. A criminal gets hurt fleeing a crime and it's not a case of 'well, if he'd not been commiting a crime he'd not have got hurt' oh no, it's usually a case of 'if you hadn't chased him he'd not of got hurt'. The world has gone mad!