There's no indication that the poster "expressed any such wishes" before the broker acted. He's just unhappy now with what happened after the fact. Again, we have no idea what the agreement said about non-complying shipments, etc...
The answer, is that unless there were instructions that specifically said what to do, the broker was likely perfectly legal to act on his behalf in any way not in violation with the law. Again, we have no idea what the agreement with the broker said or didn't say. There is nothing wrong with them signing on his behalf on its face.