It happens, my guilty pleasure is Kitchen Nightmares and related shows. Gordon and or his camera crew have been assaulted twice from memory. They get broken up crazy fast though. I wouldn't be surprised if there are more that don't make it to camera. They are trying to tell a different story in each episode, so I am sure a brawl kind of derails that story telling.

I wasn't a regular viewer but I remember some kitchen reality show where you had to beat everyone else in cooking competitions and the prize was you'd work for Gordon. At some point, one of the contestants had enough of Gordon's patronizing bullshit and challenged him to a fight and Gordon looked at him like he was a stupid child. But Gordon knows what's up. If you act like an asshole for long enough in a Kitchen, someone will fuck you up.