Waterboarding Terrorists

Someone said Water Boarding doesn't leave visible scars, but is Psychologically damaging. WHAT??? How do you mentally damage a CRAZY jihadist that believes Islam is the only Religion, and anyone that isn't a Muslim is an Infidel and MUST DIE! As a "Non Believer" I really can't believe they said that! OK, Mr. Obama and Senator McCain...Please CLARIFY for us. Which one is bad? Water Boarding an unarmed TERRORIST, or shooting and unarmed TERRORIST in the head??? We are all confused!