Interesting answer
In it you admit that human beings are quite capable of producing any one of these very complex designs. In otherwords, you acknowledge every single one of them could could be made by earthlings. So why is it you can't accept the fact that every crop circle ever made was made by people? If people can make these, they can make all of them. There's no reason to invoke some sort of mysterious origin.
So what you're left with is trying prove that any one crop circle was not made by people. Exactly how do you propose to do that?