Everything you are doing is right!
I think the problem is that from the other team's perspective, when the last place team makes a move, there is always suspicion. They assume that there is collusion involved!!! What they fail to understand is that in a dynasty setting, you aren't going to tank, simply because you have to play next year with the same team! And, i think your strategy is a good one, though he has never hit for this kind of power in his career (desmond).
Either they are suspicious, or they are pissed that a contender just got an elite bat, but the setting for dynasty leagues are different, and they need to chill out YOU DID NOTHING WRONG.
hope this helps,
C: Perez, Napoli,
1: Goldschmidt, Votto,
2: Cuddyer, Uggla
3: Moose, Encarnacion
SS: A. Cabrera
O: Ellsbury, Trout, Melky, werth
SP: Weaver, Cain, Sale, Vogelsong, Moore, Giallardo, Harvey, medlen
RP: Cook, Jannsen, Holland, Hanrahan
League: 5X5 H2H (QS)