I don’t know there are these ideas get stuck in our head and we just assume they are true for some reason. This “the capitalist will sell us the rope we will use to hang him” is prolific, its everywhere and one has to wonder why. There’s no truth in it. People would attribute it to Marx too but Marx would never say that. I think its a cultural relic that serves to make communism sound badass and scary. But hanging capitalists will not put the world on the path to socialism, if anything the opposite must be true.