No. He tried to stay out of it, then was provoked into inadvertently taking the greater evil's side. We can talk about that one quote all day, or we can talk about these three:The point of the story is that Geralt tries to be above it all, to not choose sides because he refuses to interact with evil, but instead of coming out clean he ends up doing more evil then if he had actively picked a side or pushed back against both.
“I pity you,” she said slowly, gazing at the medallion. “You claim a lesser evil doesn’t exist. You’re standing on a flagstone running with blood, alone and so very lonely because you can’t choose, but you had to. And you’ll never know, you’ll never be sure, if you were right…And your reward will be a stoning, and a bad word. I pity you…”
And...
“You’ve made your choice,” she said slowly. “Are you sure it’s the right one?”
“This won’t be another Tridam,” Geralt said with an effort.
“It wouldn’t have been. Stregobor laughed in my face. He said I could butcher Blaviken and the neighboring villages and he wouldn’t leave his tower. And he won’t let anyone in, not even you. Why are you looking at me like that? Yes, I deceived you. I’ll deceive anyone if I have to; why should you be special?”
And...
Stregobor, seeing the raised blade, jumped aside and waved his staff. “All right!” he shouted. “As you wish! But you’ll never know! You’ll never be sure! Never, do you hear, witcher?”
“Be gone.”
“As you wish.” The wizard turned away, his staff hitting the flagstones. “I’m returning to Kovir. I’m not staying in this hole another day. Come with me rather than rot here. These people don’t know anything, they’ve only seen you killing. And you kill nastily, Geralt. Well, are you coming?”
Aridea and Stregobor created "Shrike". Aridea to kill Renfri so her own children would be the heirs-apparent, Stregobor by wanting to hunt, capture, and Vivisect Renfri based on malicious rumor and theory. And where Renfri fucked up, was assuming assuming Stregobor had a shred of human decency in him that the Tridam ultimatum might work.
And what Geralt would never know, was whether Renfri would have gone through with it. Stregobor's preoccupation with whether Renfri was a mutant was never the point to begin with, it was just his excuse.