KK, I've heard several people say it with full intent. One exact quote, by a young enlisted man speaking to his buddies, "I'm going to Iraq to kill me some towelheads." I've also heard "sand *" used in this context.
It's understandable, killing another human being is not something to take lightly, and it's easier if you can dehumanize your target. Perhaps "infidel" is sufficiently pejorative to serve that function on their side. Certainly some form of this process has been around as long as warfare. That doesn't mean I have to stand up and applaud it.
Hatred of the Other, whether based on race, religion, gender, sexuality, or social class, is the central flaw of humanity.
My brother in law speaks Azeri and Turkish. He used to work in a copy store downtown and often had muslim customers come in and talk shit about America and Americans amongst themselves (in Arabic, Farsi, etc). My brother in law could understand quite a bit. One time two guys were going on and on about American women being whores, beneath contempt, etc, and my brother in law proceeded to chew them a new one in their own language. And you should hear his stories related from friends who are veterans of the Soviet occupation of Afghanistan.
Anecdotal evidence is great. I've never heard anyone who supported our troops talk about killing towel-heads or sand-n***ers. In general I think our troops and American people are about as good as you'll get. I'd much rather be looking down an American barrel than an Iranian, Russian, N. Korean, or Chinese one. I guess only a French barrel would be preferable, since it would never be fired (I'd just have to yell "boo").
I have heard plenty of insults regarding "towelhead" and "camel jockey", etc...but perhaps since I don't a know language used by Islamic people I don't hear this hatred of America you talk of here in the streets of the US. I'm SURE there is plenty of that kind of talk over in the Middle East however.
Keep in mind that we have Gitmo, etc. I don't think you can say that American hands are clean.
IMO it is more accurate to say that bigotry and racism is an unfortunate human characteristic that pervades pretty much all cultures. Anecdotes may help you bring home the anger, but then forest is lost in the trees. They help you develop nice stereotypes and the like (Such as your diss of the French at the end of your post. )