This did not require hindsight. I know I was one of a few back in 2012 BEGGING the Twins to sell high on him at the deadline. The guy was mashing in July, he screamed "I'm only going to get hurt a lot in the future", and his odds of matching that production were slim.
People, mistakenly, convinced themselves an injury prone guy with a softball player's body was going to somehow become more productive and durable into his mid-30s and be more valuable in the final year of his contract. (The argument was that an additional 2 years and 14M was somehow destroying his trade value in 2012)
Some of us were railing against that aggressively back in 2012 and, yes, clamoring for us to move him. No 20-20 hindsight required on that one - every argument made by the advocates in 2012 of dealing Willingham came true because none of it should be all that shocking if you look at his career.
I'm fairly certain that quite a few people wanted to trade him 2012. The issue at hand was what another GM would have given for an oft-injured aging slugger with 2 1/2 years left on his deal. I'm guessing not much, as most GMs knew there would be a large risk of having 2013 Willingham happen to them. If he keeps mashing, you may get a decent prospect at the deadline. I'm not sure that would have been the case in 2012.