The post-colonial movement has has led to a contemporary fervor for "de-colonizing" everything, whether for good, bad, or ridiculous. My question is: were there any anti-imperial movements in ancient Rome? There are, of course, innumerable stories of people resisting their colonization by Rome, but was there any resistance to the notion of colonization from WITHIN the Roman power structure? Were there any prominent citizens who criticized Roman expansionism on moral grounds (as opposed to it being simply too expensive, or whatever)? Or did such a notion simply not exist?
The main form of moral critique of imperialism was the idea that imperialism was morally bad for the Romans. There was a strong narrative of decline in most schools of Roman thought, contrasting an imagined virtuous past with contemporary lack of virtue, and this included an argument that empire (and aspects of empire, such as the use of enslaved labor and the importation of cultural objects from Greece) made Romans lazy and decadent/luxurious.
Romans also clearly understood that Rome's behavior involved great cruelty and could be seen as unjust, and we see this in their writings when they represent the opinions of non-Romans denouncing Rome. Tacitus Agricola 30 (quoted below) and Sallust Histories 12.69.17 are classic examples of this.
But there are no tribes beyond us, nothing indeed but waves and rocks, and the yet more terrible Romans, from whose oppression escape is vainly sought by obedience and submission. Robbers of the world, having by their universal plunder exhausted the land, they rifle the deep. If the enemy be rich, they are rapacious; if he be poor, they lust for dominion; neither the east nor the west has been able to satisfy them. Alone among men they covet with equal eagerness poverty and riches. To robbery, slaughter, plunder, they give the lying name of empire; they make a solitude and call it peace.
For more, see Miriam Griffin, "Iure Plectimur: the Roman Critique of Roman Imperialism".