All I can say is mind your own business, don't be uptight, find a sense of humor, and realize that there are narcotics out there that will do this sort of thing to people.
That may look like a bunch of soldiers just carelessly killing unarmed civilians, but you fail to see the danger of a large, disorderly, crowd of people who have lost their minds and are focused on one thing: taking down anyone in their way. In this day and age, it is entirely possible for a new disease to be created to which there is no immediate cure and has high fatality rates. Should that occur and people have to be quarantined, and they decide out of desperation to try to enter the general population, it would now be a deadly force situation and that may be what is necessary to protect the healthy.
Do I see the potential problems with this sort of training? Heck yeah, but it's not training against healthy, unarmed civilians who are rioting. I think back to the many other countries who have committed mass genocide of their own people for less. This was mostly an awareness campaign that allowed some of our military and civilian counterparts to have some fun and act out the current phenomenon: "The Zombie Apocalypse." Until you have dealt with someone who is high off of PCP, LSD, or other hard narcotics, you may never know just how dangerous an "unarmed" person can be.
Btw, I'm just putting things into my perspective. I seriously think you need to lighten up and drop your grudge against the United States. It just irritates me when people discriminate against an entire country, nation, or people group for something so... simple. And yes, I do realize U.S. citizens often do the same, and I think everyone should really be more concerned about their own domestic problems, but I am just one man and my opinion is... mine.
