You appear to have mistaken "playing by the rules" for playing within an absence of rules. You aren't being told what to do, but are choosing what to do within scope of what you
can do.
This error in interpretation leads to you seeming to attempt to justify things you consider fair and reasonable, when other people might not make that mistake and recognise a choice to behave in a way as expressly that - a personal choice made by the player.
So it's entirely feasible that other people might consider you a jerk either for your assumptions, choices and/or behaviours. So you're definitely wrong on the "can't be a jerk' statement. I'm sure you don't think you're a jerk, but that doesn't mean you can't be considered one.
I don't play GTA. Nothing to say about it.
There are many forms of 'upset'. This would seem to fit the bill, to me. I'm finding my reactions remain more on the mirthful side, which feels positive to me at least.
I give a damn about a great many things, but this particular argument isn't one of them. I don't gank, and I don't get ganked. I have no vested interest, and try to see it from both sides.
Given there's no real rules in the game, so I tend to see things are more about what fosters good, positive social interactions between folks. As in the case of OP, ganking led to this. In many cases, it leads to the reverse.
However, killing peoples ships without provocation, not caring about their response to this, blaming them for their own ships demise, and then complaining when other people explain that they consider it worthy of the ***hole tag is - frankly - hilarious.
The only real potential consequence of ganking for the ganker is that the ganked person might well consider the ganker an **hole. This seems as equally legit as the ganked person being interested in why they were ganked and doing anything about it.
Isn't hard to understand imo.