I said that the violence committed by insurgents is not being investigated for that reason. The reason more of the killings of civilians by US forces are not being investigated (at least not openly) is the same as the reason the Haditha killings were not investigated for several months. The US government does not want US voters to know about such killings, and it does everything it can to suppress this information and prevent it from getting out.

I think the only thing that has allowed this particular mass killing to get out (and finally be investigated) is because somebody made a video of the aftermath of the killings, and the US government can't plausibly deny what happened any more. You can be sure, however, that had the video not been made, you and I would not ever know about what happened in Haditha.