No, it really doesn't make a difference to your game. One player can't keep a faction in power unless they're in a very isolated area. If I came in and started running missions for another faction yours would lose control eventually because you aren't doing anything to actually bolster them.
Very true. If the cargo or exploration data of one single randomly moving around player makes a difference for somebodys BGS game, the case was lost from the start. For two obvious reasons:
1. You could actually do more good to your goal by doing stuff, than by trying to find people who might accidentally do things which could work against your goal.
2. What do you do against people who play in different time zones, on a different platform (PC, different consoles), in a different mode (PG, solo) or which the games instancing system just decides not to put into the same instance as you are?
So i agree, the whole "he might be selling exploration data which would hurt my BGS goals" is really just a weak excuse for "i want to shoot at exploration ships, as i am too afraid to go against somebody in a combat setup".