Hmmm.... they did try to embellish Thompson's intervention after the fact (He reported the incident, and led the rescue of some of the civilians), and he was also disgusted when the Army tried to award him medals for his intervention in quiet rather than publicly. While I do think it's silly that people only remember Lt. Calley (Whole platoons were involved, either actively killing or standing by and letting it happen), it's still silly to blame the whole event on one participant. I think the main coverup there was how the US Army tried to hush up the whole thing. Given the chance, I think they would have made the same attempt with Bales.

Who knows? There's plenty we don't know about these wars, and people in power tend to keep secrets, for whatever reasons they keep or give. Lord knows it wasn't the only incident of it's kind.