Nixon and Kennedy--Presidents Prone to Conspiring?

From Matthew's book, I've gathered that Nixon and Kennedy were similar in their high ambitions and ruthless pursuit of political power. An article that I recently read regarding conspiracy theories details how the two former presidents were just as motivated to get what then wanted while in office as they were on the campaign trail... In Are Conspiracy Theorists Epistemically Vicious?, Charles Pidgen writes that Kennedy and Nixon were behind some of the most significant covert operations carried out by the United States government.

After mentioning the classic example of an American political conspiracy, Watergate, Pidgen writes that "the conspiracies perpetrated by the Nixon administration at home were as nothing to the conspiracies that they perpetrated abroad"

Pidgen elaborates...

"One was the Menu program, a series of secret and illegal bombing raids in Cambodia, initiated by Nixon and Kissinger and kept carefully secret from the Congress, the Press and even parts of the military (hence an ‘event or practice’ largely due ‘to the machinations of powerful people, who attempt[ed] to conceal their role’). This helped to destabilize the Sihanouk regime, leading to the rise of Pol Pot and the deaths of millions of people. The dropping of 108,823 tons of bombs was surely a matter of some pith and moment especially for the people who were killed, maimed and blown up. (Shawcross, 1986, ch. 1.) There is now quite a lot of data on the many other conspiracies in which the Nixon Whitehouse, and in particular Henry Kissinger, played a prominent part. One intriguing example is the conspiracy to kidnap – and maybe assassinate – the Chilean Army Commander Rene Schneider, because Schneider (unlike Nixon) believed that the Constitution required the Chilean Army to allow the Marxist Allende to assume power on the obviously frivolous grounds that Allende had won the election. The general was in fact murdered and the people who did it were paid $35000 by the US government (quite a large sum in those days) ‘for humanitarian reasons’. (Hitchens, pp. 61-73.)...Another example is the eventual overthrow of Allende by Pinochet (Hitchens, 2001, chs. 5 & 6.) and a third is the coup against President Archbishop Makarios, which led to the Turkish invasion and the partition of Cyprus (Hitchens, 2001, ch. 7.)"

Next, Pidgen describes Kennedy's conspiracies...

"The Bay of Pigs was a prime example of a failed conspiracy, and Robert MacNamara recounts in his memoir In Retrospect how the Kennedy administration connived at the conspiracy to depose President Ngo Dinh Diem (the nearest thing that South Vietnam had to a democratically elected leader), a conspiracy that led to his murder and that of his brother Nhu. (McNamara, 1996, pp. 52-55.) Ho Chih Minh is said to have commented ‘I can scarcely believe that the Americans could be so stupid’, implying of course that he took it for granted that the Americans were largely responsible for Diem’s deposition and death."

I wonder what this truth is behind all the conspiracies that Pidgen tied Nixon to and also about the President Ngo Dinh Diem conspiracy? Also, were Nixon and Kennedy were indeed more prone to undertaking covert missions than other US presidents?