“Nuns with banners!”
This was a comment made about picketing of the film Monty Python's Life of Brian http://www.bbc.co.uk/pressoffice/pressreleases/stories/2011/09_september/29/holyflying.shtml but there is no reason to attribute it to Michael Palin.
Misattributed
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Michael Palin 16
British comedian, actor, writer and television presenter 1943Related quotes

“I make rude gestures at nuns”
Variant: I kick kittens. I made rude gestures at nuns.
Source: City of Ashes

Source: "Anne Hathaway wanted to be a nun" https://www.independent.co.uk/news/people/news/anne-hathaway-wanted-to-be-a-nun-2343678.html. The Independent. (August 25, 2011).

“Hearing nuns' confessions is like being stoned to death with popcorn.”

“I'm a detective, but nuns could stonewall Sam Spade into an asylum.”
Source: A Drink Before the War (1994), Ch. 2.

“Nun 1: Sir, it is only a play… with music. Do not distress yourself.”
The Baby of Mâcon

“Nun 2: (Very quietly) Sir, be grateful for the music. Most of us die in silence.”
The Baby of Mâcon
“My banner is Evangelical Truth, Apostolic Order.”
An Apology for Apostolic Order and its Advocates https://babel.hathitrust.org/cgi/pt?id=hvd.ah4gsr;view=1up;seq=5;skin=mobile, p. 262