Why do I lose karma when I take bandit things?

Why do I lose karma when I take bandit things, like objects found in some Powder Gangers camps?

Solution 1:

Those items belong to another faction, in this case the powder gangers. This is stealing, as far as the game is concerned and is punished with karma loss. The game does not take into account whether you're allied with a faction or whether they hate you and shoot you on sight, it always is counted as stealing.

Fallout morality is slightly schizophrenic, killing powder gangers is good but stealing from them is bad. You have to accept that as a quirk of the game, there is no way to make sense of that.

But don't worry, karma is not really important (Details in this question) and you earn enough karma anyway if you're playing good.

Solution 2:

Because two wrongs don't make a right. Just because you have killed a baddie does not mean you can take their stuff. The stuff could be stolen for instance. You get good karma for killing them as the "world" around you perceived them as a threat.