There was an issue in Israel recently. In Israel usable organs from the dead are given to whoever can use it the most (compatibility + health of recipient). That includes terrorists who are in need of an organ because their organ got damaged while performing a terrorist attack. That caused a lot of Israeli's to no longer opt in.

Now, whether it is better for many innocent people to die so that a terrorist doesn't live is up to you. You asked for a reason, not a good one.