Were you the bad guy? Well, you weren't the "good guy". Were they worse bad guys for demanding your loot? I believe so. In a social cooperative game, this is the type of behavior that hurts everyone.
This is why some folks complain about personal loot. Takes longer for everyone to gear as folks horde their drops regardless of how much or how little it helps them. You were completely entitled to that drop. That doesn't mean it wouldn't have been better for you to share it with a raid member for whom it's a direct upgrade.
It's been long standing policy to frown upon party members who take gear for enchanting mats or gold when it's a direct upgrade for someone else. Now we have the "personal loot system", so we have more of a "MINE!" attitude that pervades this social cooperative game...which tends to make it less social, and less cooperative. Everyone for themself.
So you have to wait a couple more days to get your upgrade. It's still there. Your 4600 dust doesn't go away. And maybe if you are nice, those you are nice to will pay it back (or forward). Maybe you tell them how much you were looking forward to using the dust, but offer an exchange like talking to the raid leader and offering to give the piece to his buddy and ask the raider leader to put you on his friends list in order to offer raid invites in the future. Maybe you'll never pug again, but maybe you will. And by helping other players you help foster a more social, cooperative, friendly atmosphere.
Or I suppose just figure everyone is going to screw you, so screw them first. Then go to the forums and ask who's the bigger jerk.