Papa John: "Let me tell some stories about how terrible other people are so I can signal how superior and virtuous I am."
Listeners: "Gasp! The fact that he tells those stories proves he's worse then they were!"
I think you are correct. Whenever someone is accused of racists comments, it is a mistake to bring up other people who have said worse. In a way, it validates the original accusations about the person's statements as they are trying to cover up the seriousness of them.
no doubt there are double standards, but other people should bring for the hypocrisy, not the person being accused.