"Occupied population?"
The first misconception that you have to get past is the idea that these are "Heroes of the People" who represent the wishes of the majority, or even a large minority, of Iraqis in attacking the coalition.
This is not true, and if anyone would do a minimum of research on this, they would find it out. These are thugs and outsiders, and a number of them aren't even Iraqi.
Not even other Shiite leaders support Sadr.