Upvote:5
I doubt very much if any prominent Roman would complain. The line of poverty was not being able to own and keep a single slave in Rome. Prominent Romans owned many thousands. About 1/3 of the population of Italy was slave. If anything gave the Romans nightmares, it was a slave rebellion. This was by far the biggest and the worst they experienced.
Slave owners would bring recalcitrant slaves to the Via Appia to admire the view. So they would understand what was in store, just in case.
Especially prominent Romans lost a lot of property because of that revolt. They would rack their brains if a worse punishment would be possible. Leniency would be the last thing on their minds.
Slave owners could do whatever they wanted with their slaves. Up to crucifying them on their property, if they so desired. Rebellious slaves could be killed, the legal punishment was crucification. As far as I know the idea of crucifying them en masse along the Via Appia was Crassus's own idea.
I think a better question would be: were there any prominent Romans who objected to the destruction of so much property? Crucifying 6000 slaves is destroying an awful lot of money.