But you don't reject the hypothesis that "Barack Obama is a wooly mammoth" because it's absurd - nobody has seriously presented it. If someone had a reason to seriously present it, then I'd not dismiss it out of hand - if only because I was interested enough to hear it in the first place, so would want to see if the speaker was making a clever joke, or perhaps needed immediate medical care. As EY might say, noticing a hypothesis is unlikely enough in the first place that you should probably pay some attention to it, if the speaker was one of the people you listen to. cf. Einstein's Arrogance