LOL, it never fails. Right around big holiday weekends, we see several posts, threads like this, talking about inconsiderate things campers do. Like already said, this is because the holiday weekends are when there is are a lot more of the shall we say, less experienced, and less considerate people out camping.
This is one of the main reasons we avoid camping on holiday weekends like the plague, like others have said. Just is not worth it to us for the extra day you get, for all the other stuff you frequently have to deal with on those weekends.
Unfortunately, though, that isn't a very realistic option for many. For many folks, the holiday weekends is the only time they can get away to go camping.
As to what I'd do in that situation: Asking to move to another site is not a good idea, IMO. You risk going to a site thats even worse in other ways. That, and frequently on busy weekends like that, IF there are even any sites still left, you will not want them, haha.
I would have told the guy something like this: "Look, I know you have a power issue, but generator hours in the park are 8-11 (or whatever they are). I'm not going to say anything as I understand your predicament, but somebody else may complain or the ranger may notice, and I'd hate to see you get thrown out and your weekend get ruined. How about you go into town, get you a new battery, and I'll try to help you put it in and get your power situation straightened out?"
..If they refuse your help and continues to run the genny, THEN it may be time to go talk to the ranger.
This way, you don't come off as the bad guy, so hopefully you won't make any enemies regardless what happens.