1. There is no possibility of the slingbox blowing out the DirecTV receiver. It simply connects to the a/v output of the box just as any other viewing device such as a TV......
2. He is correct in referance to not being legal to watch his content. It is against both DirecTV's and slingbox's TOS (terms of service) to redistribute the content to anyone other then the person(s) who's account it conncted to.
Not to say people don't do it; however it's not actually adhearing to something the account holder agreed to when signing up for service. This applies to ALL content providers platforms for distribution of their media.