One of the reasons why Shinran became the most well-loved religious figure in Japanese history is because he taught the enlightenment of the evil person.
In his time, “evil” meant anyone who couldn’t follow the moral standard of monks and nuns, which meant pretty much everyone in society other than the wealthy.
People who had to catch fish or hunt for a living, for example, were “evil” and incapable of enlightenment, even if they were just providing for their families.
In the words of Shinran in the Tannisho, “If even the good man can be reborn in the Pure Land (the realm of Nirvana), how much more so the evil man!“
He wasn’t saying we should deliberately do bad things to people, but instead that we shouldn’t judge ourselves too harshly, expecting the perfection only a Buddha can attain.
Alan Watts, for example, died of alcoholism, yet what he did for Buddhism in the West was still commendable. He was the “evil man” Amida vowed to “save.”
Shinran’s nickname for himself was “bald-headed fool.”