Is this sign real or fake? It seems quite convenient how CAIR and others are using it for propaganda purposes.

How do we know this is from Iraq? That appears to be a Real Madrid T-shirt. Are those being passed out or sold in Iraq? There is Arabic writing behind them, however that doesn't imply Iraq specifically. The thumbs up signs are just too much. Supposedly they do not have the negative connotation when used by or to Americans in Iraq, but they still are an insult in much of the world.

And, could the supposed Marine pictured be a Boudreaux, or could he be Spanish or an Arab?

As for the writing, it's already been pointed out that the abbreviation should be "LCPL" instead of "Lcpl." It's already been pointed out that the text is oriented too far to the right, almost as if to avoid the shadow. What about the other words. How many English speakers capitalize non-proper nouns such as "Dad," "Knocked," and "Sister?"

I suspect it will come out this is a fairly sophisticated attempt at propaganda.

UPDATE: I'm no handwriting expert, but this writing appears a bit too curvilinear for someone who's a native user of the Roman alphabet. Look at the tails of the 'd's. The segment in the lower right goes down at a 45 degree angle, much like the Greek alpha. Look at the lower legs of the 'K's. They're too horizontal, and they don't match the upper legs. The 'S' in "Sister" looks almost like an Arabic letter. The 'u' in "Boudreaux" is also missing a tail, making it look like the Greek letter. I also noticed a period after "Killed my Dad." However, "then" is not capitalized; most English speakers would consider that disconcerting.

UPDATE 2: Also, note the supposed Marines' sleeves. If he put his arms down to his sides, it looks like his sleeves would be an inch or two too long. Based on that and the information above, I strongly favor this being a real picture of a fake event.

UPDATE 3: The Marine and sign appear to be real.

UPDATE 4: I deleted the last comment. No suggestions of violence please. For more on comments here, see this post.