Open wireless routers were far more common 10-15 years ago, when ISPs first started pushing them. Most people hadn't warmed up to the technology yet, and security was barely on the radar; similar to what we're currently seeing with IoT.
Maybe you have no enemies and trust your neighbors, that's awesome. But, anecdotes aside, someone could cause some very ugly problems with your open wifi, without much skill or effort -maybe just for the lulz.
I feel like cheering you on for giving people free internet, but at the same time, I want to pull you aside and say "hey crazy person, please put a password on your WAP." Because, it's a bummer when bad things happen to good people.
But even if you're legally totally in the clear and don't mind the huge trouble of having all your gear confiscated for who knows how long, people have lost friends and jobs over accusations of CP or other crimes before.
I might understand why you should be responsible for an open Wi-Fi but "enough to just have your IP" is ridiculous. It is easy to hack a (D-Link [1]) wireless router. Why should you be responsible if somebody uses it for illegal activities?
Botnets use millions of devices of unsuspecting ordinary citizens.
[1]: https://hn.algolia.com/?query=d-link&sort=byPopularity&prefi...