Calley was court martialed. A friend of mine was sent from the Pentagon to Vietnam to gather the information.
I am not familiar in detail with the specifics of the two officer's actions. But, it is fairly well established that Calley ordered his platoon to round up the villagers and then they executed them, or some of them before the intervention of other US troops put a stop to it. I don't believe Calley was operating in what was known as a "free fire" zone.
The most obvious difference is that no one except jfk is accusing jfk of doing anything wrong. His superiors gave him medals. Calley was prosecuted, although there was some attempt to cover it up, IIRC.
And, based on this article, I would suggest there aren't any folks out there who are going to come forward and testify against jfk:
http://www.s-t.com/daily/10-96/10-28-96/a03sr015.htm