I'm not sure why people want to trade Hanley. People are using revisionist history in their assessments of both the Hanley and Pablo deals.
In 2013 and 2014, Hanley was worth 5.1 and 3.3 WAR, despite playing in only 86 and 128 games, respectively, and despite his poor defense. His contract is more than reasonable.
Also, in terms of the question of why anyone would think he would be okay in LF, left field is the 2nd easiest defensive position to play, while SS is the 2nd hardest defensive position to play. It's not uncommon or unreasonable to think that moving a poor or aging SS to LF will make him a better defender, if even only slightly. Outside of possible concerns with his attitude, there was nothing wrong with the Hanley contract, and there were good reasons to believe that his attitude would not be a problem. Personally, I don't think it is.
As far as Pablo goes, I was not a fan of his signing, only because I thought that for the price, there were better options, such as Headley. However, we desperately needed an upgrade at 3B. Based on his numbers from the previous seasons, Pablo should have been a significant upgrade over what we had last season. Pablo represented a key addition to this team, albeit a slightly overpaid one. Obtaining a 3B was a necessity. There is no way anyone could know whether Donaldson to the Sox was a viable option, so blaming Ben for not getting him is ridiculous.