Umm, Ron, did Nixon really say that? Wouldn't think he had the lyrics in him. Another source I just looked up:
http://teaching.arts.usyd.edu.au/history/hsty3080/StudentWebSites/Nixon%20Obits/obit9 quotes THOMPSON as saying about Nixon:

"It is Nixon himself who represents that dark, venal and incurably violent side of the American character ..."

...was he just turning Nixon's words back to himself? seems odd. Thompson never lacked for descriptive phrases for Nixon, such as:

"he was a foul caricature of himself, a man with no soul, no inner convictions, with the integrity of a hyena and the style of a poison toad." (ibid)