Alternate take: I know a couple people who support the "negotiate not escalate" thing. I'm not from Germany, but have lived here a few years, and I this is something I consistently notice: a lot of the native young adults tend to be... Sheltered? It's hard to describe, but they have a full on belief in always choosing the "correct" solution, not the pragmatic one: even if renewables struggle to power the country, forcing us to burn fossil fuels, we shouldn't invest in nuclear because renewables are safer. Even if someone is protesting life-threatening oppression and breaking things is a more effective form of protest in their conditions, they shouldn't break things because it's wrong. Even if every other option has been exhausted, a kid should never attack their bully, because violence is wrong. It's a mix of magical thinking and sanctimonious teenage thinking, but extends well into the 20s. Important disclaimer that not everyone is like this, and not everyone who is like this agrees with the examples above.

It makes them very conscientious citizens, which is one of the reasons I love living here. But it can also lead them to some seriously bad takes, such as "if we arm Ukraine we escalate the war, and escalating the war is bad so we shouldn't". The war in Ukraine is actually unique in that I'm seeing more nuance than ever from people in that age range (I guess it's closer to home than the usual problems), but it's inevitable that many will do their usual thing.

My guess is, the protest had the people from the comment you replied to, and also the people I'm describing, probably others, and a big added dose of genuine pro-Russia shitheads masquerading as pacifists.