I'm not keen on people out to just shoot others for the hell of it,
I'm pretty sure this one thing is upon which this entire discussion is based. It's all about intent.
If a player interdicts me to take my goods and leave with them, or to kill me because I have a bounty, I have no issue with that. When players decide to shoot and destroy others for absolutely no reason or gain whatsoever, I have a problem with that. Now, I'm a combat pilot, and I've never been successfully destroyed by anyone else, but it's the principle of the thing that bothers me. I was flying in an entirely unarmed T6 once, and was interdicted by a player Viper. I submitted when I saw it was a player. I immediately began typing a message as soon as I loaded into the instance, and halfway through doing that the Viper opened fire. No reason at all, he just started shooting as soon as he got a bead on my ship. All weapons full fire. I escaped, but he had no legitimate ingame reason for doing so...it was only because he could. Now, my definition for what "griefing" is is a little stricter than to include this aforementioned event into it, but I can completely understand if others feel differently.
A viper attacking an unarmed T6 with no bounties and no request for goods is, to some people, totally legit "PvP." I mean yeah, it's not against the game rules or anything, but my point is if you're the kind of person to do this, you're doing it just to be a bully and enjoy misery of others and for no other reason. No monetary gain or otherwise, and definitely not for a challenging battle. He wanted to kill me only because I was a player in an unarmed ship, and he wanted to giggle in glee as my ship exploded, though I was happy to disappoint him.
However, players attacking others for obvious gain, either for bounties or to take their stuff, should never be discouraged from gameplay or labeled as "griefing." As usual, this is a topic with two extremes, and reality lands somewhere in the middle. Some people think any pvp is considered griefing, and those few are usually the ones who cry about be attacked by anyone ever for any reason. Others think it's totally okay to shoot and kill anyone anytime anywhere just because you can and that it's completely fine. It's neither of those, but I'm willing to bet the past ten pages of this thread showcase quite a few discussing this as though it's a binary issue.