Well they made a whole movie about a plot to create clones and then never resolved who it was that started the plot. The only way to find out was to listen to interviews, so what makes you think they would follow up on this comment.

To me it would have made a lot more sense if Anakin was upset about the injustice of slavery and the lack of movement by the bureaucracy to change this. It would make the motivation for his change more believable, this would be just one of the things that sets him over the edge.

Maybe Leah has slaves? Ever think of that? Kind of takes some of the sweetness out of this princess thing.