Solas there's a difference between promising people you'll protect them and 'if you don't free these people I will take them from you'. I'll acknowledge that there's people who do not see a Tevinter without slavery, but in a similar way how many mages saw a future without Circles? Just because it looks impossible, doesn't mean it is. The hope of offering a future where one day they might be as free as anyone is one that I believe should be had, and given strength to. The thought of 'nothing will ever change, so why bother' is a dark one and not one I wish to see people have.
The Alianages need changing, and so do the Dalish but people should still have a choice. If they wish to stay in the cities or in the forests that should be their choice, and I will gladly make it so that everyone can make that choice. But do keep in mind Solas, coming to you for aid is also a choice they've made.
Pray tell Fen'Harel, what makes it any different for a former human slave to find a place for themselves then for a former elven slave? A human from Tevinter would have few options for everyone would hear their accent and where they come from and think the worst of them and they would find no refuge. They would have to slink to the poorest parts of a city, surviving on scraps and with everyone looking at them twice and not giving them second chances. Just because they are human, doesn't make their struggles less.