The problem here, from the Trader's perspective is twofold:
1) With enough bad experiences, like being killed even after dropping all cargo, a trader will naturally be forced to assume that every pirate they encounter is the worst of the lot, and act accordingly. There will be no downside to just hitting Boost at the first sight of anything that smells remotely like a pirate encounter. Not every trader will be able to escape that way, but there is no reason not to try. Why even bother taking the extra time to drop cargo? At least if you're blown up, you'll be denying the pirate your entire cargo to sort through, for the choice bits.
It only takes one encounter with the griefer side of the piracy spectrum to tar all pirates with the same brush, and you can't control the behavior of other "pirates."
2) In a game where everyone wants to have fun, what is the trader getting out of this? Sure, there should be risk... trading shouldn't be a milk run every time. But there is no fun in being asked to be the rabbit in a hound hunt. Now, there may be things coming in the game that offer the trader protection or payback. Like hired escorts or drone defense. Right now we don't have that, so it's never "fun" from the Trader side of the encounter.
I don't know how either the player base or ED's developers plan to handle this, but if the pirates want to continue having their fun playing that role, then the traders will need a way to have fun also. Otherwise, the pirates will all get ignore-listed off to their own instances, fighting each other.
BTW, I'd like to try a little of both sides in this game. So I hope there is enough incentive, somehow, for people to keep playing the trader side of this trader-pirate encounter.