The only reason you are a liability is because you can read a contract, you know the games they play and know how to play the games back.
In other words tell them how much I love their company and that they wouldn't have to worry about me leaving because I fully intend on staying put for several years - "I see this place where I can remain long term!"
But also, as you mentioned, being able to read a contract - if they get their money worth out of me after two years it is probably in their best interest, financially, that I leave.
So, in many ways it ought to be a win-win situation - I'll stay for my contracted time and you (the company) will get an experienced pilot but for a time.
It seems, though, that such common sense reasoning betrays the recruitment department folks.