You can actually bring people out to a field, make a complicated crop circle right in front of them and they'll still say somrthing like: "Sure, that one was a hoax, but some of them just can't be explained." What they forget is that until they were shown that one, they thought none of them could be explained. |
It's the usual reverse argument.
It is not necessary to prove that all crop circles are man-made, as this is the likeliest scenario.
It is necessary to prove that some aren't, this more extraordinary claim has a higher burden of proof.
It is backwards to accept the more extraordinary claim, while demanding greater evidence for the least extraordinary.