There shouldn't be any difference between e-honour and plain old honour. There's a concept called sportsmanship that everybody learns as a kid. Some people agree with it, and some secretly hate it and deep down want to abuse others, whine like babies when they lose, and cheat and pick on the weak in order to win or get thrills. Even beyond sports, it's a lesson on self control and being a "clean" adult person. Online, these people who hate it get to do what they want because nobody knows and their coach and friends aren't watching.
Ok so maybe I overreacted and didn't read the whole OP before responding reactively based on previous greifer experiences of my own, but I definitely wanted to comment on that statement of yours.
If this guy had just disabled him and opened up some kind of dialogue, then I wouldn't even be here. He just interdicted opened fire and killed. Maybe cowardly was a bit strong, but it's just not sportsmanly, it's the kind of thing that if you did on the pitch, the crowd would boo you. And if yo. I never said people who shoot first and talk later, maybe that's how it came across, but I meant people who shoot and never talk. Especially those that shoot those much weaker than themselves for no gain at all. I thought this was a case of that, and I still think it is.
Not sure what loadout the OP had, but I just assume that if he is complaining it must be because he had no combat build at all. If he did have a combat build, was flying through hostile territory, and got interdicted by fair game and lost, then I agree - nothing wrong going on here. He did say that he initiated a dialogue and didn't run or deploy hps so you can't say "oh it's really important for interdictors to not waste any seconds before opening fire". It's not like he was buying time for anything
I still strongly feel the interdictor should have said something. It's really easy to set up some autotext. It's really quite creepy to go and start a fight with someone without saying anything at all.