truth revealed

Nuns and ninjas are guerrilla warriors of the same cloth.

Please consider:

the vows!
the honor!
the silence!

They contemplate, they meditate.

The costuming: so dark and fluid. Think of all you could hide beneath that habit, beneath that headdress.

And, oh, the concealment! They live apart from society, moving stealthily, fluidly, quietly amidst it only as necessary. The training it takes to reach this level of silent effectiveness is reserved solely for the most committed of the elite.

Ninjas use NUNchuks. Nuns employ the Armor of God.

And, amidst all else their other labors, they find time to cultivate an appreciation for the arts. Sister Wendy and Splinter are two good examples of this.
Unconvinced? A rare glimpse of nuninja combat in Ireland: