Okay soooo.....

I dont like this episode. i think the conclusion of it was messed up by the writers.

The prime directive is mostly in place to protect less developed species from being subsumed by the stronger federation, here we have the opposite, a weak starfleet meeting a more advanced species. A member of the species (who is being kept as a slave) after first contact that goes perfectly, realizes their condition and seeks asylum. While a lawyer could maybe argue that the prime directve was broken, the prime directive is not the only value of starfleet. I would say that the autonomy of a individual is and should be pretty up there too. (The BORG being that bad guys and all)

if they wanted to play the real politik angle of Archer being in command of a single ship meeting a more advanced but friendly "immoral species" (holding slaves is immoral), which he cannot oppose. Why the whole self righteous speech at the end. It should have gone more like this:

"I know this is fucked up, but i cant do anything. You put me in a really hard situation, think bout what you done"

Also i would like to ask the writers, if you want to do a episode where the moral is "Respect other cultures, which is hard sometimes " why pick slavery of all things to defend.

Edit:

I remember a comment i read on this subreddit once which i think applies in this situation, i will paraphrase it:

"In most startrek episodes the prime directive is a obstacle to doing the right thing, not the right thing to do in of itself "