Real liberals still exist - except, likely they calling themselves “independents”.
They are easy enough to find- and they are worth convincing.
The Progressive/Communists/Socialists are actually a minority- but they hold key positions in academia, the media, and among some politicians and business leaders. The main bunch that we see on the streets are nitwits and violent opportunists who latched onto the slogans and don’t actually know what they mean.
Putin or whomever succeeds him will see any compromise as weakness and any concessions for “peace” will just be the slight pause for the next round. Remember how those “majority Russian” provinces came to be settled in the 1930s: by starving the Ukrainians who had lived there for centuries and the Stalin move his Russians in.
Still a sore point among that folks in that region.
Oh sure, but the classical liberal is now called libertarian. You are fighting a losing battle when you try to keep its book meaning. The liberals that want a slave nation, so they have people working for free and handing over their earned resources to the liberals unearned will argue the Founding Fathers are liberals, therefore they are the same as the Founding Fathers and they mean it. They really do believe that what they believe is what the Founding Fathers believed and that the slave nation they want is what the Founding Fathers fought for.
You’re not going to be able to reverse this dynamic. To try is to tip over windmills and you will lose. Once a nation figures how to pay for present benefits from future earnings, it’s inevitable that nation will end and something else will replace it.
Now, there is no bargaining with Putin. Now we have perpetual war because we weren’t going to allow any compromises for a real concern of the Russian people, their treatment in other countries. Had we allowed a concession, we might have avoided war or delayed it by stating out right that small territories given, for nationalistic reasons, would result in war if Putin went beyond what he said he wanted, which is to protect Russian ethnics in other countries.