So I thought about this again and it occurred to me that calling someone a piece of shit, especially in public, on their home turf so to speak, probably didn't exactly help your case.
Social networks, whether IRL or on the Internet, tend to form around certain world views, because people tend to enjoy being around others who share the same viewpoints more than they do being around those who don't.
But all world views are flawed in some way, and pretty much all of them presuppose that whenever there's something wrong with the world, it's always someone else's fault. For Christians, it's the devil's fault, for Atheists, it's the Christians' fault; for Republicans, it's the Liberals' fault, and for Liberals, it is of course the Republicans' fault.
Now I'm pretty sure that Lemmy users aren't so stupid that it hasn't begun dawning on them that killing Charlie Kirk MAY have been a huge mistake, because he left behind a legacy that none of their vitriol can ever erase, and that's not exactly going to help them win many friends in the upcoming years. But those among them who have realized this are likely keeping their mouths shut because they don't want to get in the way of the people who are nevertheless still trying to desecrate his corpse.
Basically, what you did is like going to someone's house and calling them an idiot in front of their entire family — of course they're most likely going to throw you out in order to save face, even if they secretly feel like you might have a point, simply because they want the freedom to come to the realization on their own time.
Right now, their anger is still larger than their doubts, and they're going to keep hacking away at him some more, just like they did with Kyle Rittenhouse, hoping that some cracks will appear in the clean facade. And when they don't, they'll likely just give up in a couple of months and simply never speak of him again.
They probably won't ever admit fault or seek reconciliation, and the best thing you can likely hope for is that a few them have woken up to the fact that they're friends with people who believe it's okay to murder someone in cold blood over a difference in opinion, and that's a dangerous place to be. And unless they somehow manage to convince the rest of Lemmy that this was a bridge too far, and didn't help their cause AT ALL, their best course of action is likely to just quietly leave the community altogether, the same way Lot left Sodom and Gomorrah.
But if you do want remain anyways, and try to preach the good word in the hopes that the community can be saved, I would suggest not calling them demons to their faces, because that's not going to work if the demons outnumber you. Instead, try to cast doubt on the viability of their belief system. Help them realize that if they advocate for murdering people for their opinions, they are also advocating for themselves being murdered for their opinions.