And I don't see it that way at all. 

 Ian made no true pact with Katie and Jenn. Jenn asked Ian if he would vote Tom off, and Ian said yes. But he also told Tom that he'd stick with him to the final two. Obviously, Ian was "playing the game" and lying to someone, but it's much more likely that he was lying to 
Jenn at that point, rather than Tom. Ian never admitted lying to Tom, because I don't believe he ever did. Ian just kept saying he was "playing the game", and it seems that "playing the game" in this case meant simply lying to Jenn.
 
Ian tried to explain all of this to Tom, but Tom and Katie both refused to hear it. 
 
From beginning to end, Ian, not Tom, was the most honorable person there.