The defense against Sorin's mind control, as in the game, is not letting him do it. It's essentially his "ultimate" ability, and it takes a pretty inept player to allow a Planeswalker to "ult" like that.

Normally I wouldn't even include the mind control spell, but I feel obligated to defend it out of loyalty to the source material. If it wasn't for that power, Sorin wouldn't be a powerful and popular Planeswalker.

If you let this pass, I'll give you my word that I won't frustrate you or any other player with it. As I said, I'm not trying to powergame; I'm only trying to stay true to the source material.