Yes, historical liberals advocated the violent overthrow of the ruling elite but they didn't argue that they were fighting for a utopia that required half the population to be destroyed in order to create it
LOL, Marx never advocated for the extermination of half the population. You clearly know nothing about marxism outside of Cold War propaganda.
Marxim's utopian endpoint leads to people in charge to be able to justify literally anything in the pursuit of the ideology, which basically happened in every single Marxist regime in the 20th century.
Anti-communism in the US led to millions dead across the Third World. In the name of a capitalist utopia.