They enslaved the creature for as long as they needed it, and then released it when it was no longer of such immediate utility to them. Nobody was prosecuted under Federation law (maybe that is coming later). The incident seems to have been largely forgotten. So, yes, in a sense, it has been addressed, but it hasn't been resolved legally or ethically one way or another. In a future war, would the Federation again unofficially condone this on it's ships? How far would they go? To boil it down to an absurd reduction: It's possible to torture one person to save 10,000,000,000 lives so they build a torture machine and leave him/her in it? Is war, as Abraham Lincoln said, only possessed of one virtue: it's swift ending? Or is the message in the method?
It's not that I feel the show is deliberately asking these questions in it's omission of preaching - after all, quite a lot of the philosophy that advocates different morality is not going to be overturned like that, as it accepts the suffering - I miss the show presenting what it thinks, and why it thinks that.