I've been reading Primo Levi's last book, The Drowned and the Saved, where he continues his reflections as a concentration camp survivor. It contains many lessons for anyone interested in ethics.
One of the subjects is complicity - how the Nazis designed a system to make the victims share a sense of guilt and shame - and I'm hard pressed to think of a more evil act. The SS made some Jewish prisoners participate in the killing process and then periodically gassed those crews and replaced them with others.
"Misery loves company" is the old saying, but Levi's analysis suggests that can also be "Guilt loves company." On a far less extreme basis, the peer pressure to do wrong, to join the group in questionable behavior, is frequently seen in workplaces. The person who withstands that pressure may expect attacks for being self-righteous, but what the attacks really mean is the critics are mad because the person has not joined them in their guilt.
Is it any surprise that street gangs often require the putative member to commit a crime as a form of passage to full membership?