But that's the problem, it's GLBSE's users fund. He couldn't give that money to you because it never was his to start with. He was not the owner of those funds.
Not quite.
I do however think it is important to establish the fact that doing so is not an indicator of criminality.
poor morals and character sure, but criminal, no way.
If you walk down the strip handing out all your money while drunk, later claiming the recipients stole from you makes no sense.
Your buddies might say, "man, how fucked up were you all drunk and playing santa, here is that fin back"...
but you shouldn't go to the cops and try to charge the homeless dude you also paid, with theft, for not giving it back.
It's more akin to handing a pack of bills to the wrong recipient or someone making you a payment and accidentally having an extra bill in it. He wasn't drunk and willingly giving it away and coming back saying "wait, I changed my mind, I was drunk, bad decision." Because in that example you gave, indeed you couldn't possibly expect to demand the money back as it was given to you willingly. But it's not what happened here, not counting it's not his funds on top of it.
Really, it doesn't seem like something that would impact Nefario at all as his reputation is already ruined. It would however hurt other GLBSE users for which no money will be left to proceed with paying out the balance.