All too often, people confuse groupthink with morals. With a little dialog, I suspect that we could identify some accused murderers that you would excuse.
And you're conflating moral absolutism with groupthink.
Not everyone subscribes to moral relativism, as much as you might want them to.
Groupthink would be to eschew one's morality entirely, and merely subscribe to some sort of prevailing opinion on morality. Which is ironically what you're asking the parent poster to do.