Translation:I like ninjas.
Interesting point that I'm sure many know - ninjas were essentially postmen for the shogunate during the Muromachi period. Their warfare methods were, for the most part, theoretical and more often than not they were employed to smuggle information.
But it is just like Karate, or Kungfu vs a real fight. Hand to hand martial arts had and have limited practicality. The Okinawans (karate) lost to Japanese samurai carrying swords. The Shaolin temple was burned down repeatedly- monks with sticks versus soldiers with armor and steel weapons. The Israelis learned traditional martial arts didn't work on the streets, which eventually became Krav Maga, but there's a big difference between a bare handed Krav Maga person and the mugger with 4 friends you don't see. The original ninja, just like real modern spies (as opposed to James Bond) only fought in extremis. A ninja that fought was a dead ninja- fighting a guard creates noise, which summons other guards. A successful ninja was one that completed the mission without having to fight.
I would suggest the martial arts aspect of Ninja training serves the same purpose of firearms and similar training to HUMINT professionals and Krav Maga to the average Israeli soldier- it helps to burn off testosterone so the trainee can focus on the important things- like how to spot a tail, or how to create cutouts, how to write a report for the HUMINT professional and how to use your firearm effectively, how to do a fast march, how to dig a trench for the Israeli soldier.
I believe 「忍び」(しのび) is an abbreviation for 「忍びのもの」, meaning 'one who endures'. The on-yomi reading of 「忍」is 「にん」, from which the word 「忍者」(にんじゃ) is derived. 「忍び」 is used in many historical documents, while the term influenced by the Chinese pronunciation,「忍者」, is a more recent construction used predominantly in pop culture.
I love ninjas but wouldn't want to live in their world.
Western spies and assassins just don't cut it for me either :p