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.
His statement that justice will be done (not an apology), is for the Iraqi people who love the freedom that our soldiers have given them.