And yet, we tried and convicted Japanese of torture for waterboarding.
The level of your knowledge is really .... uhhhh .... shallow. You are quoting an old Mother Jones article in which the information was taken out of context from a comment by John McCain, and then conflated in order to support a preconceived agenda.
Saying that we executed Japanese soldiers for waterboarding is like saying we executed a serial killer because he drove too fast. Yes, they waterboarded ... yes, they were convicted ... but, they were convicted of crimes orders of magnitude worse than waterboarding.
You're probably not aware, for example, that Japanese soldiers considered the liver of POWs especially potent ... and they would keep them alive while they flayed their skin, cutting off pieces of thighs, arms, ears, and eating them ... all the while ensuring they kept the victim alive for days so that they could eat the liver at the moment of death.
It is disingenuous to say they were executed for waterboarding ... they were also convicted of keeping POWs locked up ... were they executed because of that?