Can you destroy the rebels in Rome Total War?
No, you cannot destroy the Rebel faction in the way that you can destroy normal factions.
Generally, a faction is destroyed if they lose all of their settlements or if all of the men in the family die.
The Rebels are not destroyed. They represent forces and settlements not allied to any of the major factions. It may be possible to eliminate all Rebel forces and settlements on the map, but more Rebels could appear later.