The ethics of the boot

I was running a dungeon today and encountered an ethical situation I had never been in before.  Normally when the group kills a boss and checks out the loot he dropped it is rolled randomly to see who will get it.  If someone really needs it to use they get it, and if not then the game randomly hands it to someone who will then presumably sell it for a small sum of gold.

Today though a boss died and a rogue in my group grabbed the item as if he needed it.  I looked at him and noticed that not only did he not need it, he did not need it in a truly over the top, egregious fashion.  His current item was a good 80% better than the one he had snagged and there was no possibility of his not being aware of this.  I called him on it and told him to roll randomly to distribute it.  He responded by equipping the new item for 30 seconds or so and then putting on his old, drastically better item and continuing with the dungeon with a "I think I need it" excuse.  A few minutes later another item dropped and again he just grabbed it with a flimsy excuse.  Again I checked and found he did not actually need it and was just straight up stealing.

At this point I was getting pretty pissed off.  I told everyone else in the group that he is stealing and that I wouldn't stand for it.  Once a dungeon starts I basically have two options if I want to get out of this situation:

1.  Boot the offender.  I can't do this until 15 minutes have elapsed and I have to get the rest of the group to vote to boot him.  The votes are private though, so I have no idea who votes for or against the boot.

2.  Just leave.  If I left my group would be totally wrecked and would just die.  They would have to find someone new and restart the whole thing from scratch.

I told the group that a boot was incoming, and when the 15 minutes had elapsed I started a vote to kick the rogue.  One of the other people in the group told me to quiet down and just deal with it since the amounts he was stealing from us weren't very large, and when the vote came back the others had let him stay.  We ended up finishing the dungeon and the rogue stole another item when the final boss died.

So here is the question:  What should I have done?  Voting to boot a thief is certainly right, but when the rest of the group refuses to cooperate I can either finish the dungeon out and accept being stolen from or just quit the run and watch they rest of them die and have to restart.  The challenging part for me is that there are two people in the group I am quite happy to desert and leave up the creek and two I don't know about.  The thief and the person who defended him on the basis of "Stealing is okay if it isn't much" can rot for all I care, but the other two people in the group may have voted the thief out, I have no way of knowing.  I know that the thief himself and his supporter voted to keep him, so the remaining two votes are lost.

Is it ethical to inflict unpleasantness on two people who may or may not have done anything to deserve it in order to do what I feel is right and to inflict reasonable punishment on those who have wronged me?

It is much like my struggles with capital punishment when I was younger.  When I was a teenager I was all for capital punishment figuring that if you commit premeditated murder it is totally reasonable to forfeit your life.  I still don't have any issue with that penalty, but the issue is not the penalty but rather the certainty.  We convict people wrongly sometimes.  Not often, but enough that there is no justification for capital punishment.  It is better to remove that option completely and incarcerate forever than to kill a very small number of people unjustly.  In this case of video game crime I am in the same situation in that I know what I would do if I had all the facts, but I must admit that I do not.