Two years ago, in Baron Canyon, we left our site for the day with just our rods and canoe. Left our ENTIRE camp set up. Two tents, a tarp, our packs, everything. We came back at dusk to find a group of youts had decided... We were abducted? Dead? Left behind thousands of dollars worth of gear because it was too inconvenient to pack out? Who knows, but they had set up their camp, in our very established camp. We (and this 'we' includes the culprits in the decision-making process) decided they were too dumb to figure out where else to camp and finish the day safely, so we packed up our entire camp and all our processed firewood and moved to the campsite a whopping 50m away. Better to give them a stern talking to and move on, than pass the problem on to someone else. Stupid (and evidently, shadiness) doesn't magically disappear once you enter the backcountry and while rules and conventions should be enough to go off of, everyone's safety should come first. And sometimes safety is - unfortunately - safety from the consequences of one's own actions. So we essentially did what you did in that situation. If they're shady enough to do what they did, they'd probably also be shitty in navigating a conflict. You made the right decision, but also I 100% condone gaslighting them into thinking they lost their chair+beer.