Browbeat or other "punisher" card interactions with planeswalkers
He would be allowed to redirect the damage to Sorin.
Even though the Sorin player chooses whether to take damage or to let the opponent draw, Browbeat is controlled by whomever cast it. The Tibalt player controls Browbeat; so when Browbeat would deal damage to the opponent, the Tibalt player can choose to deal that damage to a planeswalker that opponent controls instead.
Daniel Kitachewsky
L3, Paris, France
Rules NetRep