I met them yesterday. They are role-playing a band of thieves in that area, and they have senses of humor. If you stop hating them for a moment, and talk with them, you might see they are only having fun and can be very nice about it. While i was there, Hugs apologized to a passerby for taking a shotgun and offered to return it. Then Hugs told us "she" felt guilty about that one. So a thief with a conscience. And Hugs in particular is a non-combat character, so i don't exactly see Town Control in her future, nor any power-leveling on molerats, floaters, or ghouls. She sneaks around and peeks into your inventory - takes stuff yes, but otherwise is friendly.
If you tangle with a thief, first try being polite and simply ask for your item(s) back. Just try it - it can lead to some interesting conversations, and potentially a new in-game friendship. Laugh at how corny that sounds if you want, but it's true. If they don't just give all your stuff back without a deal, then make a deal! "Why should i have to make a deal with a thief to get my own stuff back?" Well, you don't have to, but do you want your stuff back or not? Such arrangements can lead where you never expected. For example, when I told Hugs I make Buffout, she immediately green'd me and thanked me for stimulating the economy. Now that made me laugh. She asked me if I would bring her some Buffout. I made 1500 Buffouts before, so I had no trouble giving this poor druggie thief a few buffouts. (I assume she likes them for their savory flavor). Well that's it - instant new friend right there. When I see her stealing in the future, I'll say hi, stop and chat. Maybe their thieves guild will give me tips about secret stuff in the game. Who knows! But you miss out on all of that if you hate them all, and don't even try.
A thief was messing with me in Junktown once too. Someone different. He blocked me in and I was unable to shove him aside. He demanded payment to move. So...i calmed down and decided to play along. I asked him how much he wanted. He told me 1000 caps. I said that was unacceptably low and I demanded to pay more. Lol. He was confused. He said no, all I want is 1000. I said no deal haha. I told him my freedom was worth a lot more and I would insult generations of freedom fighters if I agreed to only 1000 caps. We stood there looking at each other for about 1 minute. Then he ran off and I was free. Why he didn't take more caps, I'll never know, but if this had not happened, I'm sure I would not even remember being there that day.
It's these role-player characters who add some depth to the game and create the most memorable moments.