First off, your league is terrible for having a league vote on trades. Leagues should be set up to have the commish approve trades, not the league. People get trigger happy in leagues set up like yours because they don't want other teams to improve. Those types of leagues are communists and you might as well not allow trades because every time a trade is accepted, people hit the protest trade button.
The trade may favor one team, but as long as there is no collusion (cheating), the trade should NOT be vetoed. It is not up to other owners to manage your team. If I were you, I wouldn't join that league again next year. Find a real league to be in!