Why is Obama catching heat for Libya?

Why are so many people upset about whether or not Obama asked Congress to attack Libya? Obviously people don't remember their government and civics classes because, constitutionally, the president can attack anybody he wants without permission. The president need only ask when officially declaring war against another body. Similar to the last unpopular "war" in Vietnam. Why do people bash Obama so bad anyways? He's only picking up the mess left by W.