Well, if people were mad, then you should have vetoed it to begin with. You should let people vote, and then veto the trade based on the vote. However, the people who joined the leagues knew what they were doing when they joined. They knew it was set to Commish, so if they had a problem with it, they should have expressed it then.
In our league, we vote, and if 2/3 vote one way or the other, it goes that way. If less 2/3 agree on the way the vote should go, then I (the Commish) get to decide.