I think there's a lot of signs pointing to Jayce actually doing the right thing ...or at least the right thing based on the information available to him at the time.
We can't know for a fact just how much Viktor was changed and what his healing was doing to the people who came to him in the long run, but considering all the hints dropped by the writers, the situation is much less clear than we think. Obviously, everyone's first instinct is to condemn Jayce and his actions, especially because Viktor is one of fan favourites, but looking at the teaser for the next Act and what little we know about what happened to Jayce, I think it might have been necessary evil.
I think this scene of Viktor temporarily 'possessing' Salo in order to talk with Jayce points to just how fucked this little community that Viktor created actually is. There's a reason why everyone's getting those 'it's a freaking cult' vibes.
This scene made me more uncomfortable than anything else this season and I think it's clear that it was meant to make feel that way. There's something so uncanny about Viktor's voice coming out of Salo's mouth, especially paired with that look on his face and how Viktor seems to be able to see and experience things through him in this moment.
And then there's also the issue of all these people dying a horrible drawn-out death as soon as Viktor himself 'dies'. Yes, they came to him on their own, they asked to be healed, but did they really know what they are getting into? Did they know this is what might happen?
Some of them were already dying, true, but Viktor healed all kinds of people, some of whom most likely had their whole lives ahead of them. He, knowingly or not, inevitably sped up this process. Not all of them were consummed by Shimmer-addiction or permanently disabled like Salo.
And then there's also the fact of all of them basically abandoning their previous lives to serve Viktor and his community. Which, okay, makes sense, there's certainly a parallel with the community that Ekko created for Zaunites to keep them safe from Piltover and Silco's plans. They made an informed choice, though, and I don't think the same can be said about Viktor's cult-like commute.
They seem peaceful, yes, but also devoid of personality and entirely dedicated to Viktor and his cause. Of course, it can be explained by gratitude towards him and desire to be kept safe in a calm and peaceful environment, but it's taken to such an extreme point that it definitely crosses the line into uncanny territory in my eyes. Their hivemind behaviour is very unsettling and even though Viktor seems to frame his recent actions as some kind of greater good, I don't think it's necessarily true.
We have yet to find out what Jayce saw and who's in the right and who's in the wrong. Either way, as usual when it comes to Arcane, it seems to me that more than ever, everyone's a victim of the circumstances and tragedy spares no one.
Considering that Viktor is set up to be 'reborn', I can't help but wonder what it means for his community and if they will also be brought to life by whatever connection they have with him. It would be a fascinating choice given how Viktor's arc has always been about autonomy and making your own choices.
Arcane, it's been a pleasure having my heart torn out of my chest by you. Can't wait for the last Act.