That's exactly my problem with blocking, which is a much more viable mechanism for harassment and griefing than ship to ship combat.
Switching to Solo or a tightly curated PG is the only way to avoid the blocking effect, of someone my CMDR is instanced with, from excluding all of those instanced with the individual being blocked. Natually, this is just as problematic for my own, primarily coop, organic play, where I enjoy encountering random CMDRs I don't need to have met before, as it is for yours.
The only thing a PvP ganker can do (if they get phenomenally lucky) is destroy my CMDR's ship. This is a negligible financial burden in a game where a single wing mission will pay a half-dozen rebuys, and costs only minutes of travel time. It's also a potentially enjoyable interaction, and something that can be countered, contextually, in-character.
Blocking is anonymous, has no contextuality, and a malicious blocker can potentially cause issues for a wing of coop, or mutually competitive, players in Open for hours on end.
I don't automatically associate a superficially unprovoked attack upon my character with an attempt to cause greif to me as a player. Frankly, I'm not sure why someone actually trying to grief me would bother attacking my character when there are vastly more bothersome means on hand that have no counter, and essentially no chance of being enjoyable.