they're not using liberal in the american sense of liberal meaning gay blue haired woman with pronouns and vegan lattes that conservatives get mad at (in general theres a lot of queer vegan women with pronouns and colourful hair on hexbear); they're defining liberal in the marxist sense in that its people who support capitalism but arent currently fascists, so this includes conservatives, neoliberals, social democrats, and all sorts in it. Their comment seems to be applying more specifically to the ideologically committed liberals as opposed to mostly apolitical people who just say, "oh yeah i guess i;ll vote democrat this time" once every 4 years and have that be the extent of their politcal consciousness

Liberalism

Some more resources:

On Liberalism

• Why do communists dislike liberals?, 2
• What about free speech?
  • How do communists feel about free speech? Are they okay with suppression of free speech in places like China?
  • What does free speech really mean?
  • What are the different types of free speech?
• Why do leftists think that FDR co-opted the left to "save" capitalism?
• What's wrong with democrats ( insert moderate party here ) ?
  • Why not vote for the lesser of two evils (Lesser-evilism)?
  • Can't we change the democrats from within?
  • What about "moderates" like Jimmy Carter? Can't we push them to change?
  • Can't we use voting to solve our problem? Is violence really necessary? What about Martin Luther King Jr. and Gandhi? audiobook
• Malcolm X on liberals.