According to the original source (and Wikipedia), Zyklon B was apparently used on people's clothes after those were removed, not on sprayed directly on people,

According to the original source (and Wikipedia), Zyklon B was apparently used on people's clothes after those were removed, not on sprayed directly on people, so it's not exactly the same. There are pictures of Mexican laborers being sprayed on the head with DDT in the 50s, however, and that for sure was not healthy (nor was the general treatment... humane to begin with). I don't think we need a very stretched comparison with the Nazis and Zyklon B to easily affirm that the US Army and the US Government did many times horrible things to plenty of people, including its own citizens (and especially the black ones, see e.g. the Tuskegee syphilis study)