I really could care less how many iraqis die. And if it was just a matter of pull out and let them fight until they are all dead I would have no problem there either. But what would happen is a war between the shites and the sunnis and one side or the other would win, probably the shites as they are more numerous and supported by iran. An iranian style and controlled government would be established. terror camps would be set up and pressure would be put on syria and saudi arabia. Inserection would begin in those countries and jordan as well. The sunni's will be subjigated and the caliphate will be established.
The only way to prevent this is having US troops in iraq and building up a strong iraqi government.
Also the media supports the islamists by showing only the attacks and murders there, many reports of which are false. This is done to reduce the will of the American people, something you have obviously fallen for yourself. The islamist know that Americans won't stand for a long drawn out war and the democrat victory makes them think they can win if they keep up the assaults. They are using the lessons of vietnam and the dems are buying right into it. The overall strategy is to draw things out as long as posible until the US gets fed up and leaves. Then like vietnam we will see slaughter, but on an even grander scale.
The mistake with going after saddam was assuming the iraqis would unite around the US and join together to rebuild their country. The second mistake was allowing sadr to live and re-establish himself.