I'm not sure where are you reading the word "all". The activities we require our CMDRs to do in Open are the following, copy-pasted from FUC rules:
- Preparation, Expansion and Fortification
- Undermining and Opposing expansions
- Any BGS activity in PowerPlay relevant systems
As you can see there's no mention of PVP. I'm repeating myself but we will try to kill enemy CMDRs no matter the game mode they're in. We'd kill them in Solo if we could.
Also, every game is about winning but most people still abide by some simple fair play conventions that make the game better for everyone. Doing Powerplay as a mindless merit grind done in Solo with no opposition removes most of the tactical aspect of the game and favours the factions with more manpower. After all these years we don't expect the Aisling community to play fair so it's all good, don't sweat it.