This is why it is very hard to fully discount the government lying through their teeth about things. There are tons of other examples, but this is the big one since it directly impacted Americans on American soil and is within the lifetime of many (either the study itself or the much later Clinton apology that brought it back into the national limelight).
And when we talk about varying health results by race, we often want to talk about poverty and access while ignoring that black Americans, especially in the South, are aware of Tuskegee and have a mistrust of many medical treatments due to it. It makes it much easier to spread conspiracy theories and makes them much more believable, that is for all races.