Yes, I have been confronted with that situation before, but in the end, the need and greed rules are nothing more than a gentlemans agreement.
Technically, he was in your group and as such he was doing his job and had the right to roll, even if he had not any use for it at all. It was not nice to do it, but there isn't any rule against it.
Ignore him and be done with it.
True its a Gentleman's agreement, but if enough people add that ninja to their ignore lists, his SWTOR life will start to get really lonely. Just saying.