'Destroy shadow' destroys all shadows because you haven't picked the right/wrong one yet. You have only checked for a condition which is True, and it destroys (all).
Instead of that condition, you should use System -> Pick by comparison -> Select shadow and add that condition (peerid =/= myID). See if that works.
And if that doesn't work for some reason, try setting ALL of the shadows to Invisible. Then: System -> Pick by Overlapping point -> Overlapping with player -> Set Visible