If his car caught on fire, insurance would cover it. Pioneer owns you nothing for the wire. They have no control over that. It's not up to them to do the wiring job. The wire should have been fused somewhere, and that fuse should have blown if the power wire ever shorted to the chassis. Now if the HU itself started on fire, that'd be a different story, but that's never happened, ever, as far as I'm aware. Crap wiring has happened a lot. Always fuse your power wires.