I've given the report itself a quick look. its interesting how the focus has been on some of the specific answers to questions and not the overall findings of the report.
From what I saw of the central findings, longer tours and more combat equalled, on average, more mental health problems. I believe that there also seemed to be a connection between the same characteristics of combat/tour length and increased the propensity for ethics violations.
I think that this report highlights an operational dilemma for COIN and other similar operations. There is always a refrain that forces need to be engaged longer in these types of operations so that they can really learn and understand the culture, environment, etc. This argues for lengthening unit deployments. The flip side, however, seems to be that longer commitment has the downside of greater "moral fatigue" and thus threatens to undercut the very advantages of prolonged engagement--which argues for shorter deployments. There's probably a sweet spot in there and its probably different based on the duties associated.
COIN is naturally morally degrading to the force. Outside of just the torture argument, without strong leadership attention, a force that is continually engaged in COIN is likely to slip down to the level of the foe wrt consideration of civilian casualties, etc.
One of the interesting findings is that transition team personnel tend to fair relatively better than their brigade combat team counterparts. I wonder if that's due to the level and character of their engagement with Iraqis--they are apt to develop a greater, less sterotyped regard for the people (people as in the Iraqi population) that they are fighting for.
The classic "men in combat" discussions emphasize that the troops really fight for one another, not for the stated national causes. In COIN, if taken to an extreme, this can be counterproductive to the mission itself. The bond of brotherhood can become more important than protecting, or considering, civilian lives. I would venture that the closer a unit operates within the community and with Iraqi forces, the more chance that those elements (population and allies) will be considered closer to the scope of the brotherhood to be treated with a similar emotional bond.