There have been some strong feelings about backfeeding, legality, safety & liability. Found some strong similar views in the associated Electrical Forum. Also found this:
"Exception: Temporary connection of a portable generator without transfer equipment shall be permitted where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the normal supply is physically isolated by a lockable disconnecting means or by disconnection of the normal supply conductors"
Regarding - "When it comes to electricity, never trust anyone, not even God!
"- that's why you learn to always check the circuit & not take anybody's word on it being OFF
Regardless, if you don't know what your doing, this shouldn't be done