How do I talk to my cousin who believes conspiracy theories?

I have a cousin (who I care about very much) who has gotten very into conservative American media in recent years to the point he has gone down the rabbit hole of believing in New world order/cabal types of conspiracy theories centered on Jews controlling the world. The other night we were visiting and he was like "well if you take away the German accent and angry tone Hitler made a lot of sense." He went on to say that a secret cabal of Jews control the world and need to be stopped. He is convinced Trump is going to "roll back the curtain" on it all.

How do you help a person walk back from that far fringe back into reality?

• A little background. His mom (my aunt) and her family are Palestinian Christians and have no love for the Israelis, who took away their homes and kicked them out of Palestine (which is why they moved to the US) but the whole Hitler thing is a bit next level.