Although you have to wonder what it says about people who choose to enter any form of conflict with another group while hiding behind these mechanics to protect themselves from what would be ingame reactions and try to remain anonymous doing it.
What it does do though is justify so many PvPers claims that PG and Solo shouldn't exist as it does not create a level playing field in allowing only 1 form of defence or attack being Solo and PG PvE grinding only.
Personally as a PvE player who accepts that PvP is part of the game as are player factions, attacking people even economically from PG or Solo smacks of cowardice and has the same impact as an exploit.
I'm all for non PvP modes, but using them as a way of safely attacking a PvP group doesn't seem right to me. If you are too scared to meet them and fight them on home turf, then you shouldn't be able to hurt them.
And before the obvious comments start (and just to make sure I get moaned at by both sides) I would expect the same in reverse so if a PvP group wanted to attack a declared PvE group they would have to accept that the PvE grind is the way to do it and they can't insist the PvE group change their game to suit them.
But for an aggressor to hide behind game modes so that their attacks are secret and not take what would be the consequences of being the aggressor is just plain wrong.
easy fix, make your own game and set the rules you want.