So I'm just wandering away from Sanctuary near the beginning (another restart) and before even going to the Red Rocket I find a farm to the West. They're nice enough and I finally learn about Caps for currency (was wondering if that would every come up in the game). Anyway the guy said that his other daughter was killed and some raiders took her locket and asked if I could get it. Sure, why not so off I go.

Well I clear the raiders and bring back the locket. Now this farm is being listed as a Settlement in my Pipboy and it says that it's looking good except it's low on Defense.

Now wait a minute ... when the hell did I say I would take this farm as a settlement or would want to be responsible for them? Now I got to put up some turrets around their place (short circuit boards right now) or they might get attacked.

Is this going to keep happening? I do something nice and all the sudden I'm responsible for them? I know from prior play-throughs that the Minute Men like to set up settlements and such, but my character hasn't even met them yet. Was this supposed to be a MM settlement or something?

Thanks.

You do not need to build Defenses for every Settlement, but I have found the Minutemen Questline can be simplified by adding anything a Friendly Settlement needs as early as possible in the Game. Turrets just are faster and easier than building Beds, Guard Posts, and other Items needed to attract Settlers to man the Guard Positions.

Well you can have 1 settler manning 3 guard posts I believe, maybe more.

But the OP is saying he shouldn't be responsible for a settlement after he does one favor for them. Like he doesnt owe them anything and the game is pushing it on him.
I agree it is silly and there are a lot of freedom to roleplay or make any of your own decisions besides where to go at what time, but most of your choices and story decisions as well as certain feature are thrust upon you or already cut out for you

Yes, that's what happens If you want to avoid it, ignore all quests that start from a farm.

And it looks like the Minute Men questline sends you to random farms to do their quest, but you can do that without the Minute Men too.

So once I join the MM will this farm just automatically be added to the MM settlements? Kind of feel like I put the cart before the horse.

The MM settlements are only MM settlements in your head. If you want, they're just your settlements.

Edit: for clarification, I mean that nothing distinguishes a "MM" settlement from another.

Yes, there are only your settlements, regardless of if they join you when you do their quest on your own, or when sent by Preston. Or make your own in a place where there is no quest required.