This is the stage where he needs to read an in-depth study of any revolution. His theory has to be tested against the challenges real-world revolutionaries faced.
Imo the Russian revolution is the best one to study but it's more important that the source is good. Losurdo's Stalin is a good read. Proles Pod is in the process of a multi part series as well.
Rather than try to directly refute years of ingrained propaganda, start the process of building a better foundational understanding. The misinfo will be slowly abandoned when it starts to contradict his more complex network of knowledge.