In this day and age, any posts not clearly labelled as sarcastic should not be treated as such. There are plenty of people out there who, as you said, would believe it without question and spread it like gospel. Unfortunately, there are enough of them where you can’t give them the benefit of the doubt any more. There absolutely are people who would read and disseminate it and turn it into the next big conspiracy theory that somehow Joe Biden would be held responsible for because of his relationship with Genghis Kahn. Or something.