Basically prisoner's dilemma.

I think the answer is inherent to the question of whether it's "justified", and the fact that you're being downvoted.

If Prisoner's Dilemma is played once, the optimal strategy is to defect. If it's repeated an unknown number of times, the optimal strategy is tit-for-tat.

Now, if you're an identifiable actor in a pool of tit-for-tat-players, and you have a history of defecting first, you're going to face opponents who normally play tit-for-tat start to defect against you first, too. In the end, you will end up as one of the worst peformers in the player pool.

So when you're asking if it is "justifiable" to defect in a game like this, it is the same as asking "will I be treated worse if I defect in this game". The downvote confirms this, I think. It means that in this population pool, bad behavior is punished (or people pretend it is)

Now, if defecting can either be done secretly or if you're in a popluation pool where everyone defects anyway, then always-defect is probably the nash equillibrium. In that case, defecting will be seen as justifiable.

That logic is how every atrocity in human history was enabled:

- If I catch this escaped slave, I can get the bounty instead of someone else!

- One of us Auschwitz guards will shoot that escaping prisoner; why shouldn’t I get rewarded for it?

So on and so forth.

Not only that, but if some people have ethical and moral considerations about the consequences of x, then those people have an ethical reason to actually do the thing, since the alternative is that the people doing it are those with no ethical or moral consideration.

If a piece of technology is going to be 90% bad 10% good and you can push it to 80% bad then it is completely justifiable to go for it.