Here's another intuition pump, then:

How many of you boosters thought that it was a good idea to quarantine the astronauts who returned from the Moon? Raise your hands please.

Now why did you think that was a good idea? We already knew about the vacuum on the Moon, the temperature extremes, the UV radiation, as well as the requirements for life on Earth, not to mention the fact that pathogens on Earth have been honed by millions and millions of years of evolution to prey on the particular biochemistries found on Earth. According to biological theory at the time, there was no way that life would be found on the Moon. But they did it anyway. They weren't crazy, were they?