For Rome specifically, the practice of slavery in and of itself was never questioned on a social scale outside of individual slave rebellions, although Christian Rome made many strides to improve the conditions of slaves. Even still, slavery in Rome could take many forms, with slaves being treated in widely different ways. Unlike citizens, a slave could be subjected to corporal punishment, sexual slavery (Prostitutes were often slaves), and could be tortured and executed (Although it was illegal to kill a slave without just cause, what exactly defined just cause was up to debate). They could not own property, but could work property of their master in his name. They could be educated, and some could even be allowed to own money, which they would use to save for their manumission.

The prospects for a slave being freed were actually pretty decent, as long as you weren't a farm laborer (They were treated very harshly, as if they were farm equipment). A slave would often be freed upon their masters death if the master willed them their freedom (which was considered the socially acceptable thing to do if they had served well), and educated slaves would often be freed earlier than that. Freedmen were then granted citizenship, and could pretty much do everything but hold public office or become a senator, and many became extremely powerful and wealthy.

I had asked a similar question a while ago - Were there Ancient Romans or Greeks who disapproved of slavery?

While some Romans advocated for more humane treatment of slaves, no one criticized the institution itself. While each slave desired their own freedom, they do not seem to have ever questioned slavery itself. There was no such thing as a human-rights movement or an abolitionist movement in Ancient Rome, not even the early Christians disputed the notion that some people were servile by nature and thus it was right to enslave them. It is interesting to note that, when Spartacus led his fellow slaves to their escape from servitude, they did not embark upon a campaign of liberating their fellow slaves but instead turned to plundering the countryside.

Could the Serville Wars be considered social movements?