Bukkit

What steps will reproduce the problem?
1. tame a horse so that its yours
2. let someone else attacking it using a bow
3. arrowentity does damage on the horse

What is the expected output? What do you see instead?
nothing should happen, because they are protected

What version of the product are you using?
v1.3.0 for 1.6.2 Jul 15, 2013

Do you have an error log of what happened?
no errors in the console

Please provide any additional information below.