We don't need to submit moral justifications for how we act in a video game, do we? I mean if you want to attack another player, no rules are stopping you in open. There is a lot of defending this position, in these terms. Why would anyone have to justify how they see the actions of other players in a video game?
If it's cool because the rules allow it, it's cool right? Across the board? Choosing any one of the three modes is cool, because the game allows it. Right? Attacking the mythical unshielded, empty, T9 is cool because the game allows it. Right? Blocking a player you don;t want to spend game time with is cool because the game allows it. Right? Skulking around an Engineer's base is cool because the game allows it. Right? Menu logging on an attacker is cool because the game allows it. Right?
The point here is you can't have it both ways. Open has made it's bed. Now they have to lay in it. Strict attention to the actual rules of the game will indicated that FD are ok with players avoiding PvP. Because FD made PvP non-essential to how the game is played. That fact is demonstrated by the rules FD apply to us all.
Lobby for the rules to be changed, that's totally ok. Trying to enforce some kind of 'space bushido' over the actual rules is folly, and only leads to frustration. If ganking is possible, it will happen. Nothing will change that, so fortunately, we are given a way to just ignore that type of player, no matter which mode you are in, or what sort of allegiances one acquires in game.