This is why I prefer commissioner veto over a league vote. I like to ask the traders what their rationale is for trading if it seems one-sided.
I also like the idea of having two assistant commissioners that also have input on trades. The trade goes through if two of the three commissioners ok it. If one of the three is involved in the trade, then both of the other commisioners have to say ok, and if two are involved, it's up to the third.