The 5th Kansas Cavalry did have a reputation as a "rogue" regiment, as did some other Union regiments -- the 1st Colorado Cavalry comes immediately to mind. Invariably, in those cases, the quality of the commanding officer was the primary determinant of the character of a regiment. In the case of some Kansas regiments, the chain of command either actively encouraged roguish behavior, or looked the other way when it occurred. At one point, the military authorities in the Department of the Missouri forbade Kansas troops from crossing into Missouri in "hot pursuit" of guerrillas because of their excesses, and even went so far as ordering troops to the Kansas-Missouri to stop the Kansans. One Kansas regiment (it may have been the 5th Kansas -- I'll have to check) was kicked out of Missouri and ended up in Arkansas.

But John's point was that you can't paint the picture of abuses with too broad a brush, and I agree. There were numerous cases where commanders of U.S. troops protected civilian property and court-martialed (and even executed) violators. Cases can be found where U.S. troops actively assisted southern civilians with rations and other supplies.

On the other side of the coin, the record is full of reports of Confederate troops stealing from their own civilians -- "descended like a plague of locusts" was a phrase often used -- not to mention more heinous crimes, such as murder and rape. You should look at some of the Confederate court-martial summaries available in print and in the archives. It'll make your eyes pop. And that doesn't include the barbarous activities of southern guerrillas, home guards and other irregular units.

As you said, war does things to soldiers. War provides soldiers with the opportunity to display noble self-sacrifice and heroism, as well as an opportunity to engage in abject depravity. And war is an equal-opportunity employer, affecting the soldiers of both sides.