A better analogy is:
I leave my door open with a welcome sign out the front.
Two people enter.
One of them picks the pocket of the other.
And then the thief blames the guy who told him about the open door in the first place.
I don't find it particularly troublesome that maps of open WiFi networks exist.
I do not, however, think that it's okay to behave maliciously, or inappropriately on open WiFi networks.
My earlier response to your comment about hoovering plain text passwords didn't properly acknowledge the bad behavior that took place. I concede that you are correct, it was rude and insidious behavior.
It was never the connecting that bothered me, it was the storage of the data encountered.