This guy is the MVP of white nonracists. He's got a name, a back story, and even a family. Obviously Griffin thinks he's kind of a big deal, because almost no one else gets this kind of treatment. East is probably the most important, or at least most memorable (for good things), white man in the book. Griffin describes him like this:
I knew of one white man in Hattiesburg to whom I might turn for help—a newspaperman, P. D. East. But I hesitated to call him. He has been so persecuted for seeking justice in race relations I was afraid my presence anywhere near him might further jeopardize him. (10.267)
So, immediately we know that he's a special guy. He's a white journalist just like Griffin, but he has been so persecuted because of his activism that Griffin is afraid to even talk to him. What's even more impressive? Despite all of that, he still helps Griffin without even blinking an eye. That's an impressive dude.
He's kind of like a mentor to Griffin, and spending time at his home reading his biography gives Griffin the determination to finish his experiment. Instead of running away like he wanted to at first, he heads right back to New Orleans after spending time with East. But if Griffin is trying to follow in East's footsteps, then we know what's going to happen even before the book ends. He'll end up ostracized from his community for telling the truth.
Finally, it's worth noting that East is one of the few white guys in the book who's not scary. Actually, Griffin humanizes him by talking about his family (check out the Family Theme for more about that) and showing that he's just a regular dad. Here, he shows a cute interaction between East and his daughter,
She did not approve of her father's avid watching of westerns and children's programs, and he insisted that he be allowed, by God, to view his "favorites." (11.8)
Aww, so this guy is basically the world's best humans. He's a stand-up dude, totally moral, cute with his kids and likes Saturday morning cartoons? Dang. We want to go to Hattiesburg to chill with Mr. East.