Kenya is to hearts what Irisa is to pain: Irisa cut down Elah Bandik even when they were throwing rocks at her, because she couldn't understand why they had to live that way. She was probably right, but it was none of hers, and Bandik died anyway. Kenya's doing the same exact thing for the same exact reason -- love and compassion -- and it's going to fuck everything up for both of them.
Walker Percy quoted Flannery O'Connor in one of his weirder novels: "Tenderness leads to the gas chamber." I struggled with that for a long time, maybe ten years, coming back to it every now and then to see if I'd changed, become horrible, or if the sentiment had changed, become comprehensible. I still think it's creepy to link those images to religion, which both of them were doing. But in the end, I think this is basically what it comes down to: The second you start establishing yourself as the moral authority, rather than something outside yourself, you start making decisions based on what is going to make you feel like the Good Guy. And that does lead inexorably to hell, because people weren't designed that way.
We all make choices all the time: Irisa is clearly headed for a massive choice, and when she makes it, it's going to be personal one way or the other and the consequences will no doubt be game-changing. But you gotta be pretty out of Tao to look at an entire culture and think you could do better: Cultures are self-creating and self-regulated; they don't just drop out of thin air -- they're stones, formed by rivers and by time. The Defiance experiment isn't about forcing change on people, it's about integrating all of them into one and you can't do that by chopping things off -- demanding that people deny their nature in order to uphold the fantasy -- or else you will end up with gas chambers, or North Korea, or the Cold War.
It's cool for Kenya to feel possessive and protective of Stahma -- and she'd agree -- but once that warps itself into ripping Stahma out of the river, it threatens the entire world. Not just in the marusha sense, but in a practical one too. Look at Irisa: Her parents had already jumped tracks -- out of Irzu's light and into a fresh, new, synthetic cult -- when Nolan found her, so he didn't even have to chop anything off, right? And it's still killing her. And how beautiful would Stahma be, without the web she's spent her entire life learning to weave? Being without a seeming, why, she'd become nothing at all.