A primer on the assassination of American presidents

Lord have mercy! Is JC Wilcox completely bananas? He claims that presidents Lincoln and Kennedy were assassinated – and Reagan almost assassinated – because they were trying to protect America from foreign countries and, in the case of Lincoln, for opposing  a new world order.
John Wilkes Booth was staunchly pro-slavery and believed that by assassinating Abraham Lincoln he could revive the Confederate cause. The assassination had absolutely nothing to do with foreign affairs.
John Hinckley, who attempted to assassinate Ronald Reagan, was a nutcase who in his sick mind thought he was proving his love for actress Jody Foster by attempting to kill the president.
While there is endless debate about the Kennedy assassination, Bob Woodward of Watergate fame and one of the best investigative reporters in the world, said Lee Harvey Oswald acted alone and that none of the conspiracy theories hold up to intellectual scrutiny.
Who do we believe? Woodward or Wilcox?
Eric Bahrt  
Chiang Mai