The problem is really alternatives. Give into Russias demands and they will do the same again soon. It will also send a message to China for example and make war more likely in the long run.
What kind of peace agreement would you see possible?
Btw if you’re interested on the topic of the risk of nuclear war related to Ukraine there’s a good video by Lonerbox in which he also explains the logic of the side you’re arguing with here in more detail.
In my experience it strongly depends on the organizers. The latest pro-palestine rally i attended was organized by some leftist organizations in coalition with local palestinians and that rally worked out very well. Some conspiracy nuts with signs how Jews rule the world were told to fuck off by some Antifa guys and everything else went very well. Also no national flags besides palestinian ones were allowed, i appreciated that a lot.