This is a well known story to those who look into such things but the bulk of the public knows nothing about it.
After World War II the US government was (to put it mildly) out of control. The new Security State abandoned all ethics and believed they had a moral imperative to do so. They believed the moral position for the new Cold War (largely generated by the United States I might add) was to fight from a position of moral supremacy without ethics. One is left in despair when an attempt is made to reconcile this way of thinking.
Actually it's not too hard. The nation is god and must survive at all costs. Anything is permissible as long as it perpetuates American power and greatness.
This type of thinking quickly succumbs to the calculus of the slippery slope. Every potential scenario is imagined and must be countered. If you're thinking of it, so must the enemy and a programme must be developed to counter it.
It quickly spins out of control and situations arise wherein (you hope) someone asks, "Just what exactly are we doing?"
Having lost the forest through the trees, the US engaged in a multitude of vicious crimes against humanity. The experiments in Guatemala are but one small chapter. As is the case today, there are some experiments and exercises easier to conduct outside US borders, beyond the reach of US law enforcement.
The story is much bigger. It wasn't just syphilis and gonorrhea but radiation and many other experiments that in some cases were so pernicious that the CIA scrambled to destroy the evidence. Some of these chapters cannot be re-opened. Many seeming exposes are in reality exercises in damage control.
The Guatemala experiments are but one chapter or outworking of the ethical imperative that led Washington to recruit a host of former Nazis. While many have heard something of the story, few have really looked into it or grasped the scale of America's collaboration with former members of the Third Reich. They were recruited in the realms of science, medicine, industry and espionage. They became critical components of the American Security State apparatus developed for the Cold War.
At the very least it was calculated that the Americans had to utilise them so that the Soviets would not. This kind of tortured ethic leads to the horrors and crimes that took place in Guatemala. And of course racism played no small part. Elitist Americans could shrug their shoulders. Using brown people as lab rats was no great crime, right?