Advanced technology of that era that can wipe memory and implant Romulan remote-control into people's brains can certainly alter personalities as well. That doesn't make it ethical or justified (think Kurn, Geordi...) Of course the villains aren't concerned about being evil. Has that ever happened? Did they ever have to be? So Riker opposing a cruel culture is a terrible message? And that speech is very much the point of the whole episode. She exists not only to suffer, to show how cruel these people are and how the victims are effected, but to speak for her group and expose what happens to them. I find it quite odd to see her as "just a plot point". There is a lot of dialog with her and Riker, she doesn't just have a minor victim role. Sure, the apparent hetero-cis-normativity is as outdated now as Pike's "woman on the bridge" and Lester's "women can't be captains" is. It would be interesting to check earlier script versions, maybe it got lost in rewrites.