I sincerely doubt any Jedi would say anything like that. Much more likely they would point out the practical impossibility of stamping out slavery everywhere in the galaxy, a task that even a galactic government that outlaws it can't manage, much less a relatively small order of monks. No doubt they'd be happy to oppose it when practical, they just know that stopping the pratice is beyond their capabilities, however great it would be if they could.
Agaim, extremely doubtful. A Sith might tell a group of slaves that if they want their freedom, they should fight for it and earn it for themselves, but only if they just happened to be around some slaves complaining about their lives and had no other interest in them. And they wouldn't help them, just make the remark, probably with dismissive arrogance because of their own belief that their percieved "strength" makes them superior to these whiny slaves. But Sith are quite happy to enslave others whenever it benefits them - see the Empire's treatment of Wookies for just one example.
At the end of the day, Sith "philosophy" is entirely self-indulgence. It references the concept of freedom as a contrast to the more restrictive philosophy of their adversaries, but it's not remotely about that; in the end it is always strictly about pursuing their own gain and, at best, not caring about the effect of their actions on others (at worst often actively prefering to achieve their goals by harming others).