Not going to get drawn into the whargarble anti-Open-PP arguments going on here, but jesus... I'm not sure you can ask for much better evidence than this video. Our PvE (Open only!) hauling players were even involved in all of this, mostly running the gauntlet while people interdicted to defend them.
As it turns out, the only people
not in Open were some of the Imperial players who chose to log into solo and private group to attempt to oppose our expansion while their factions' PvPers died in Open. Funny how that works... if our PvPers had lost, our haulers would've died (we don't swap to solo or pg), and their private group / solo underminers probably would've successfully opposed us. Meanwhile, their PvPers (sometimes narrowly) losing these fights seemed to have little effect on their undermining speed.

Open Only would at least level that playing field of cause and effect. Commanders who can't deal with what even Frontier says Power Play represents shouldn't be in Power Play hotspots.