He was explaining to me how if the main breaker on his panel was not shut off the electric would go out the service entrance cables to other houses for his niehbors to use.
This is partially correct.....and very stupid.
It will go down the lines, the neighbors may see it although they wouldn't benefit much from it unless you're talking about a huge generator.
The problem is that it will go up the pole and 'backwards' through the transformer where it will get stepped back up to several
thousand volts and be waiting on the line to kill the innocent lineman that is trying to fix the downed/damaged power line so he can provide for his wife and children.
What you've described is dangerous,
potentially lethal in fact, and very stupid. A transfer switch is required to verify that when the generator is running it can't be backfeeding the lines. In case it isn't already clear at this point, backfeeding the lines is very, very bad. I don't care what ideas he has to the contrary, it may as well be attempted murder. If the right set of circumstances comes along, the murder will be more than attempted.