Only complete idiots think it's dangerous to ride with headphones.
The rulemeisters did get one thing right:
Rule #66 No mirrors.
Mirrors are allowed on your (aptly named) Surly Big Dummy or your Surly Long Haul Trucker. Not on your road steed. Not on your Mountain bike. Not on your helmet. If someone familiar with The Rules has sold you such an abomination, return the mirror and demand a refund, plus interest and damages.
Only complete idiots need to use mirrors.