Well my husband has OCD (its severe and only mildly controlled by meds, he is on a very low dose because of a demanding job) and he sometimes becomes obsessed with strangest topics (usually read somewhere), I just roll my eyes lol Now I sometimes have to warn him not to bring XYZ topics at a party. He usually does ok but I also usually sit by him at parties and kick (not hard lol) him under the table if he forgets. Lol lol

Actually my dad likes crazy topics too. Ignoring it is the best approach