Still this?
The ONLY reason people should be 'killing' other commanders in this game is if a) They're consenting to it b) They have a reasonable bounty on their heads, or c) they become aggressive during a piracy transaction.
A is not valid, you are playing in open, you automatically consent to whatever can mechanically happen in open. Just like most online games, Elite: Dangerous is also rated.
"Online Interactions Not Rated by the ESRB" - Warns those who intend to play the game online about possible exposure to chat (text, audio, video) or other types of user-generated content (e.g., maps, skins) that have not been considered in the ESRB rating assignment.
User generated content also including what players do.
And no, it isn't called ganking, that word is being misused often.
Ganking is several small people teaming up against a big target.
Griefing, is the term you are using for. Attacking others for the joy of attacking others to disrupt their play style.
Blowing up someone is entirely alright, the problem comes from people deliberately doing nothing else and only against those that clearly have no chance of defending themselves, absolutely nothing to do with PvP, but in itself, the act of destroying someone else, is perfectly valid.
Kinda like if there's free tastes somewhere and you take everything so no one else can taste, it is not illegal (though some places have 'one only' now) but it is an incredibly anti social, disruptive and annoying behaviour that would not be accepted and would have consequences irl, but not online, because of the nature of the internet.
But unfortunately it is posts like this, that OP is referring to, when a PvP focused player tries to discuss the subject at hand.