Everyone was doing it
There have been many moral lapses leading to our current cultural moment. Immoral behavior will not go away. Dr. Albert Bandura of Stanford University has studied the psychology of moral reasoning for decades. He has identified eight mechanisms that people use to rationalize immoral behavior.
Soldiers learn to see killing in the context of a larger good; terrorists may say they are punishing "nonbelievers."
"Collatoral damage"; "clean, surgical strikes"; and having someone "taken care of" are all familiar examples.
Comparing an enemy to Hitler to justify an attack; or excusing a reckless act by comparing it to a worse transgression by a rival or predecessor.
Displacement of responsibility
Shifting the blame to a boss, a leader or another authority figure; "I was just carrying out orders"
Diffusion of Responsibility
Sharing the responsibility for a transgression with others who took part, or who played indirect roles; "Everyone was doing it."
Disregard or distortion of consequences
Refusal to acknowledge the reality of the damage caused; rationalizing that "it wasn't all that bad".
Assailing others as degenerates, devils, savages or infidels. Some torturers refer to their victims as "worms". The people being cheated or attacked are "asking for it".
Ahh, that we might fully admit we are all scoundrels at heart (even the most "civilized" of us), in need of redemption, and with the courage to say, "the buck stops here".