Now I’m trying to think what would be the equivalent of the “liberal” insult in my country… We hear a lot of you’re the “extreme left”, just as bad as the extreme right. You’re “outside of the republican/democratic frame”. As in you’re too radical too be part of the “polite democratic society”.

The “liberal” insult coming from a right winger would be used in a similar way to what you describe there, but to a leftist “liberal” is also an insult in a very different sense. Leftists basically use liberal as a derogatory for people that aren’t far enough to the left. There’s a lot of nuance to it in the way that the term is used now, but that’s the kind of the gist of it.