The apology is for the Iraqi people who want freedom and a democratic society (which is still the vast majority).
As the mom of a soldier who just came back from Iraq, I have anecdotal evidence that the Iraqi people LOVE the American soldiers. I'm sure many of them are bewildered by what they've seen ( a very few of) our soldiers do.
This will help the good Iraqi people understand our military, our President, our society, and our purpose.