I’m glad you let the spiders live. I understand the point you are making about agnosticism and atheism. But I am agnostic not in the sense I am about domestic arachnids because the proposition ‘there are no spiders in the house’ is falsifiable. I can find one. The proposition ‘there are no gods’ is not falsifiable. At least, there is nothing humans can do to falsify it to the same standard you would in relation to spiders.
You are an agnostic in the same sense I am in relation to thousands of gods in which others believe or have believed: Odin, Thor, Zeus, Krishna. You cannot prove they don’t exist. But I bet you don’t say ‘it’s entirely possible’. In fact, whatever you philosophic view, you are an atheist in relation to these gods. I’m the same, only in relation to one more god than you. The same applies to fairies, ghosts and banshees. Can’t prove it, but no, I don’t think they exist.
On the fools question: be in no doubt that those who have not concluded there are gods would think themselves being labelled fools by the use of that quotation. Your philosophic justification that the words ‘there is no’ are open to the interpretation ‘I can prove there is no’ would not immediately occur to us.