Preston Garvey is famed for sending players on endless settlement liberation quests. Often, these settlements will be threatened by raiders. Incidentally, the latest Fallout 4 DLC lets you become a raider. You see where this is going, yes? The first thing that popped into my mind when I started the new DLC was, "What would Preston Garvey do if I took him along for the ride?" Most of the time, Preston is fine with you taking quests and going around the Nuka World theme park, even if he might disapprove of smaller moral choices. But if you take over an actual settlement as a raider with Preston Garvey as your sidekick, he will lose his shit completely, as you'll see below in the footage by FluffyNinjaLlama:
"I trusted you, and then you joined up with the scum that prey on the Commonwealth?" Preston asks, before basically disowning you as a general and friend. Damn, dude. I was just giving you more territory to claim during your radiant quests, chill!