Update: read this book if you like reading about the naive white knight fighting the "ideology" and "oppression" of the religion on the world. sigh. Just what I need, another liberal lecture.

While he does rescue the girl, the main reason he does it is still selfish. He uses her to get information in the city, register in the guild, etc which he doesn't want to do in his name. Having strong feelings about slavery after witnessing it for the first time is only natural but he doesn't make it his life goal to change the ways of this world. If you read the next chapters you will what you wrote here is not correct.