Games that foster positive interactions have significantly less amounts of griefers. See Deep Rock Galactic for example. No one likes bullies.
Lack of forced PvP (ED has forced PvP because the only mode, open, which has the option to meet strangers without third party tools doesn't prohibit it) is not the reason for griefers to exist.
Griefers exist because of human psychology, of the necessity to vent out frustration, the desire to make others as miserable as their life (in their perception) is.
Sure, ED is not designed around as a playground for those griefers, but inadvertently enables griefers due to the nature of the game's possible interactions.
Such unwanted interactions are fortunately mitigable by the set of tools provided to the player, but they are not impossible.
So you understand that there is a need for balance and games can be optimised to favour or deter particular playstyles but not eliminated them completely in an environment where players can interact (even if that's just a forum & not in the actual game, there's plenty of killers on this forum).
Each individual does not fit into only one classification, and many display traits of all four types. It also varies depending on mood etc, I've had this discussion (and taken the test) several times over the years & in general I am more explorer & more killer than I used to be.
You say that no one likes bullies, but a lot of people do enjoy seeing a bully get their comeuppance, and killers do that too. I don't enjoy getting sent to the rebuy screen by another player (especially if it seemed embarrassingly easy for them) but I enjoy denying them that pleasure enormously. Without killers out there trying to stop me my game would be much less rich.
ED appeals to Griefer types, and it seems clear to me that is intentional. The game designers create hotspots (CGs, engineer systems etc) where players are motivated to gather socially (because it's fun), and as an intrinsic part of that social gathering people will be targeted by killers (because it's fun).
If you want to be able to meet lots of other players, not all of those players will like you or be nice. If you go to a rock concert you have to keep your wallet safe from pickpockets. If you want to go to a hotspot in open you have to be prepared for confrontation, even if it's just someone complaining that you are sat on the pad for too long, or you feeling that the Cmdr on the pad is deliberately ignoring the queue waiting to dock.
The game needs killers/griefers/gankers. Not too many, but not too few either. It offers plenty of ways to avoid them too, but in avoiding them one must accept that they are removing opportunities to be sociable too.