If I lend my neighbor my rifle and he kills someone or something that wasn't legal to kill, it isn't my problem - as long as he was legal posses a firearm. This isn't the same as sharing your IP address.
A shared IP address can be in use by me and my "friends" on Tor - at the same time. A rifle is only in the hands of one person at a time.
If you put a phone booth on the street in front of your house or business, like a free phone booth, are you liable for the contents of the calls placed on it? What if there were two phones? A hundred?
What if it wasn't a phone but a mailbox? A big chalk board? A bulletin board?
What if it weren't a mailbox but a free parking lot? Bob could put a thumb drive in his glove compartment, park his car, and then have Alice pick it up. Am I liable for what's on that drive because I provided free parking that was used as a medium for illegal information?
That why I think sharing things with strangers cannot logically make you liable for their speech and information.
Having a free-to-use shotgun and a box of shells in front of your house is an entirely different question. That's why I said the analogy was a poor one.
A shared IP address can be in use by me and my "friends" on Tor - at the same time. A rifle is only in the hands of one person at a time.