Two Wrongs Make a Right is a fallacy in which a person "justifies" an action against a person by asserting that the person would do the same thing to him/her, when the action is not necessary to prevent p2 from doing a to p1. This fallacy has the following pattern of "reasoning":
This sort of "reasoning" is fallacious because an action that is wrong is wrong even if another person would also do it.
It should be noted that it can be the case that it is not wrong for p1 to do a to p2 if a is done to prevent p2 from doing a to p1 or if a is done in justified retribution or in self-defense. For example, if Sally is running in the park and Biff tries to attack her, Sally would be justified in attacking Biff to defend herself. As another example, if country c1 is planning to invade country c2 in order to enslave the people, then country c2 would be justified in launching a pre-emptive strike to prevent the invasion.
Peter Arnett: "Now, the United States government says that you are still funding military training camps here in Afghanistan
for militant, Islamic fighters and that you're a sponsor of international terrorism.... Are these accusations true? ..."
Osama Bin Laden: "...At the time that they condemn any Muslim who calls for his right, they receive the highest top official of the Irish Republican Army at the White House as a political leader, while woe, all woe is the Muslims if they cry out for their rights. Wherever we look, we find the US as the leader of terrorism and crime in the world. The US does not consider it a terrorist act to throw atomic bombs at nations thousands of miles away, when it would not be possible for those bombs to hit military troops only. These bombs were rather thrown at entire nations, including women, children and elderly people and up to this day the traces of those bombs remain in Japan. The US does not consider it terrorism when hundreds of thousands of our sons and brothers in Iraq died for lack of food or medicine. So, there is no base for what the US says and this saying does not affect us...."
(From an interview with Osama Bin Laden by Peter Arnett)
Notice that Bin Laden never addresses the question of whether he sponsors terrorism, instead simply turning the accusation back against the accuser. Even if all of Bin Laden's accusations are true, they have nothing to do with the question, and thus are irrelevant.
Bill has borrowed Jane's expensive pen, but found he didn't return it. He tell's himself that it is okay to keep it, since she would have taken his.
Jane: "Did you hear about those terrorists killing those poor people? That sort of
killing is just wrong."
Sue: "Those terrorists are justified. After all, their land was taken from them. It is morally right for them to do what they do."
Jane: "Even when they blow up busloads of children?"
After leaving a store, Jill notices that she has underpaid by $10. She decides not to return the money to the store because if she had overpaid, they would not have returned the money.
Jill is horrified by the way the state uses capital punishment. Bill says that capital punishment is fine, since those the state kill don't have any qualms about killing others.