In Italian there is a juicy idiom when somebody gives a risible explanation: knowing that children can delude themselves and try to deceive others when playing hide-and-seek,
they say: "... hide oneself behind one['s] finger".
Is there a set phrase (I mean one everybody recognizes as such) in English? Can you think of anything more appropriate than "making puerile excuse[s]---"?
That is the nearest I could find, but I fear is not a set phrase:
We cannot hide behind the puerile excuse of 'since we can't be perfect, we should not even begin'. That's little more than NRA-speak for don't .
The child in the picture is playing hide-and-seek, he is deluding himself he can't be caught; a finger is even smaller than a post.