For the record, Ryan Hanigan is better than Salty in every aspect of the game except power (even has a higher WAR since 2009, although he has less games played), is an elite defender per both SABR and scouts, and is cheap.
Since the Sox' main catching prospects aren't ready for 2014 and Butler and Lavarnway aren't good enough to start, the move only makes sense, since he could move on to a mentor role to Vasquez come 2015. This isn't groupthink or whatever else you can come up with to justify your thought process, it's common sense.