Because questioning the existence of aliens on Mars is exactly the same as denying a well-documented, extensively researched, and universally recognized historical event like the Holocaust. How could I have been so blind? Let me just whip out my time machine and bring you firsthand evidence. Oh wait, it seems to be out of order at the moment. My apologies, I guess we'll just have to rely on the countless testimonies, survivor accounts, photographs, documents, and mountains of irrefutable evidence that already exist. But hey, I'm sure that pales in comparison to the burden of proof for extraterrestrial life on the Red Planet. Let me get right on that for you.