John Lewis' boycott of the inaugural isn't unprecedented, nor the reason for it: He also boycotted G. W. Bush

WaPo reported this Sunday, Jan. 21, 2001, here:

Some members of the Black Caucus decided to boycott Inauguration Day; John Lewis, for instance, spent the day in his Atlanta district. He thought it would be hypocritical to attend Bush's swearing-in because he doesn't believe Bush is the true elected president.