I can vouch for it, it is very very effective, I discussed with a friend whom believed that a cabal of jews control the world and other one whom believed that the earth is flat
It should be noted that it is not easy to do, you need to have foundational knowledge of these topics and quick historical references to people/historical characters whom also made the "mistake" of believing what your interlocutor did, that way you can both set a reference for your interlocutor so he/she doesn't feel alone and as an outcast, and thread a narrative needle through history itself showing how people used to think that but now don't because of x, y, z evidence, think it like James Burkes idea of linking different topics through history, if anybody is interested I'd very much recommend listening to the Dan Carlin James Burke podcast episode and then checking James Burke books on it
But as OP said, I very, very much have enjoyed the conversations with "them" as I see them basically as adversarial journalists of sorts, asking some very tricky epistemological questions to which the foundations of modern science, history and modernity itself are built
And lastly a key, "There are no Good Great Men", everyone whom got to power in history is basically by definition Not A Good Person, and that is because just to get power at all one must play dirty most often than not. There are are just a very few select people whom we might look as being "Good"