Then the issue is with a lack of PG tools to remove inactive players?
Yes, I had their admin for Mobius PvE Eurasia on my friendlist and we talked some times at CGs.
It's a PITA you don't have admin tools, so for Eurasia he was solely responsible for aforementioned 12500 members.
Actively vetting is impossible in these circumstances, as are quick reaction times. Mobius took several days to be acknowledged,
and god forbid Saberius was on vacation. This is what PG people say when they want tools for administration (like squadrons).
On the other hand, it seems someone over at Team Mobius needs to step up and be a bit more pro-active as I think that's going to be the best solution, long term.
See above, it's just not possible. Word of mouth by the way is powerful, you don't find a ganker thread here or on reddit without mentioning Mobius.
There is SPEAR. A group that is dedicated to counter criminal behavior by players. For them pirates are also criminals that must be hunted down. So there more or less a RP Police Force, not limited to anti-gank.
And they sometimes gank themselves (as my squadron had first hand evidence). Still the best and only ganker deterence out there.
Except, well, most gankers love to fight, so they are actively helping the gankers by hunting them. A bit borked, but hey.
Aaaand the ones who don't want to be speared (

) simply block them. Spear has an available public certified player ATR list, similar to the Distant Ganks list. No one hindering the gankers to block the hunters.