Yes, they're annoying, yes they're carebears who prey on mission runners, and yes most of them are cowards and won't fight 1v1. These things we know.

But I thought of it like this. If you pop an NPC and the wreck contains loot - they can steal it. Stealing constitutes taking items from a container that do not belong to you. Salvaged components are items. Salvaged components are contained within a wreck. And yet when someone is salvaging your wrecks and not looting them, they don't get any punishment for it. What it comes down to is them using a module to take your items from a container that you created by destroying an enemy. Anywhere else in EVE this is illegal and results in an aggression countdown. Why not with salvaging? Because some Dev somewhere wrote "CONCORD considers wrecks to be communal junk, anyone can have junk"? Seems legit...

And then of course we move on to everyone's favorite - the real reason its an exploit. Let's say you choose to fight back. I've one shotted many a T1 frigate or destroyer and gotten away with it. 99.9% of the time they either return with a PVP fit ship and a few friends, or all of their friends who were waiting warp in and gank you, you loose everything. My point here is there's nothing - literally nothing you can do about it. You can attack - you might pop one or maybe two of them, but you'll be ganked, scrammed, and pop goes your ship. You loose.

Or you can give in, just let them have all your loot and salvage. They'll make lots of money, you'll have wasted a lot of time and lost isk. You loose. It seems a poorly balanced system where the people making their isk legitimately have absolutely no recourse or defense against having people blatantly steal from them. They want you to try to defend yourself so that they can exploit a game mechanic and have people warp in and kill you, which you would have absolutely no defense against. Balance the system, make it a fair fight.