We had a similar situation in the beginning of the year in one of my leagues in which i was commissioner. I beileve it was...alex cintron and joe nathan for keith foulke (inactive manager gave Foulke). This was in April, when nobody had any idea what Joe Nathan would do by the way, and at that time we were like 'holy christ-nuggets, what a robbery, the guy gets Foulke (who at the tiem was thought to be a top 5 closer) for cintron and a guy whos never closed games before...numbers aside the big issue was that one manager obviously didn't really care what he was doing to his team, which I believe is what you are complaining about here.
So we did this...I sat down and did some numbers projections..there really wasn't a BIG difference between Nathan and Foulke...we figured Foulke for 45 saves and nathan for 37 or so, so it was cintron for 8 saves...not that bad...
so i suggest you do some projections for the rest of the way and if the numberse are simliar let it go...personally i think the guy getting bonds loses...but anyway if the numbers projections are close theres nothing really wrong with the trade in my mind.
Incidently...people say that collusion is the only reason to veto a trade...I disagree, though it is the BIGGEST reason to do it...in THIS case it looks like collusion, i.e. the only way to get an inactive manager active is to ask him "hey i proposed you a trade, would you go and accept it" but if the numbers are similar and the trade is fair, whats the big deal?
Again, incidently, you said yourself the manager proposed a fair trade, so why did you vote against the deaL?
Rest in peace Mitch Hedberg. I name my fantasy team "Buoyancy of Citrus", in your honor.