Translation:I like ninjas.
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 「忍び」 is used in many historical documents, while the term influenced by the Chinese pronunciation,「忍者」, is a more recent construction used predominantly in pop culture.