Fake is his fate. A walking talking hollow man, stuffed not with straw, but with popular culture.
Why is he going after McCain?
The Dude perceives a threat from McCain from beyond the grave in the person of Manafort and Kilimnik, the Russian spy, so he is hitting back. It is all he knows how to do. He was deceived by Manafort, who promised to get him what he wanted; Manafort, the world-class adviser, who turned out to be the snake in the garden incarnate. Can the Dude admit he was duped?