[quote=@Lord Coake]
[@Korbanjaro]The Railroad tells the FO4 PC several times that the lives of Synths are more important than any person, so I doubt they would be focused on saving humans from slavery.
[/quote]

This is true, but there's a context to be kept in mind with that - In the Commonwealth, there are not slavers who traffic in human "goods." This situation is not even part of their purview, especially considering their proximity to The Institute. The closest thing to traditional slavery that they would have contact with would be The Pitt and Paradise Falls, both of which are thought to be resolved by the time Fallout 4 rolls around. (I don't know what the "canon" choices for both those situations are in the Fallout Universe, however I assume they are meant to be resolved by the player as "slavery is bad, so put a stop to it.")

If The Railroad suddenly found themselves dealing with not only The Institute, but also Caesar's Legion grabbing up their agents, I can imagine that priorities might start to shift, considering their loyalty to their agents and predilection towards retribution.

It was a moral situation that would prove interesting, either forcing a paradigm shift of sorts to maintain a moral high ground, or damning them characteristically to being basically being as single-minded and thoughtless as any other faction without a conscience.