I literally found a friendly Enclave soldier in one of their mini little outside hideout (on a broken bridge which is near that sugar-bomb-ghoul).

He had a rocket launcher and I was able to sneak up to him and talk to him! He said something like "Hey, how's it going?" and the only option was "See you later".

He only attacked me when his other two buddies attacked me... So what's up with this?

Idk, but for instance if you glitch into jefferson memorial when the enclave are there they will all be friendly aswell

yeah i also i have him friendly for me, he just is. i try not to kill him but its difficult.

Yeah, I’ve noticed the blue tick on the radar at that outpost, but I was never curious about it before now. I see friendlies quite often among hostiles, sometimes going back and forth from red to blue. Mostly on Raiders and Enclave, but it has happened on critters, too. My characters are pretty simplistic and don’t worry about it, they just kill everything.