who's responsibility is the runner at second advancing to third?
 

The base ump is making the call on the batter runner. Yes the base ump would have a call on a throwback to second on R1. However, the plate ump would have R1 going into third. Ifthe Plate ump had called obstruction andbelieved the runner would have reached third had there been no obstruction then I have no problem with the plate ump making this call... that probably wasn't the case but I wasn't there and could have been the case and the fan/coach writing the question might not have seen the plate umps call.

reported that one too