If thats true then leaving your wireless network open also means your inviting people to use it and thus users of your network can't be charged with hacking.
And you shouldn't be charged with hacking, just like you aren't charged with grand theft auto if you take an ulocked car that had keys in the ignition.
A user of a file sharing program may not have the intend to share his files.
That is not how peer to peer software works, for the most part. The onus is on the user to not share things they don't want to share, anything that's shared is shared to the whole world, government agents included.
I agree with the content of your second paragraph.