In other words, the reason that they haven’t expelled ISIS from their city, is because the people of the city support ISIS.
Bomb the whole damn thing.
Now, if the Shia Arabs come, they will crush the Sunni ARabs and may be kill them. If the Kurds come, then the Arabs fear a renewed Persian Empire.
If you are a secular Sunni Arab, you will have to lie low in Raqq (which some seem to have done) and may hate the Islamic state, but you will still fear the Shia Arabs and the Kurds
An analogy would be like a German Lutheran pastor with his wife and daughters in a town to the east of Berlin. assume he opposed the Nazis, was briefly jailed etc.
In 1945 he would be terrified of the Soviets coming and what they would do to his family. If he didn't have the option of fleeing to the West, he would have reluctantly fought with the Nazis.