The mythos of the liberals is way more personnalized, usually assigning moral failings to people who disagree eith them, something like "those people are dumb enough to be manipulated, we ought to explain thing slower/better" "we are on the reason's side". The fondamental attribution error is probably the fallacy for which liberals (authoritarians liberals especially) are the most susceptible to.
For the leftist movements, the mythos will either go to a marxist or neomarxist "We oppose the billionaire/landlords/owner class, and must struggle together to put it down, educate yourself and those close to you" or to a more generic anti-system mythos.
Furthermore, the left is often egalitarian, and the "traitor in our rank" mythos is mobilized to explain why you are not above X depite being (genetically for nazis, culturally for fascists) superior.