Originally Posted by
dcg 
I think he or she means that people are quick to point out character flaws in others but are unable to see their own. However, the saying you posted is pretty much doing the same thing, so I don't know.
Not really. There's a significant difference between recognizing torment from other people for what it is, and tormenting the tormenters. One might have imagined that this distinction is or would be obvious.
The slave may dislike or even despise his master, but that's not the same thing as the slave wishing to enslave someone else. And certainly not the same thing as actually doing it.