Has that ever been proven? I suspect it's as unproven as the theory that Tor operators are "common carriers" and as liable for the traffic that passes over their connection as an ISP is for the traffic that passes over its connections.
which was written by my colleagues at EFF. (It doesn't mention particular legal theories that may help exit node operators, though I think CDA §230 and DMCA §512 might be among the laws you're thinking of that have historically protected ISPs, since ISPs have resisted being classified as common carriers in the U.S.)
At the very least, you can get your computer and networking equipment seized. Tor's own FAQ says you shouldn't run exit nodes at home:
"Should I run an exit relay from my home?
No. If law enforcement becomes interested in traffic from your exit relay, it's possible that officers will seize your computer. For that reason, it's best not to run your exit relay in your home or using your home Internet connection."
