plaster saint

plural plaster saints

1. Someone who makes a show of being benevolent and morally upright, often in a hypocritical way.
2. A model of correct behavior.

   Of course, I don’t want to make [prison] officers into plaster saints; and they themselves would not want such an absurd depiction.

   2017, Theodore Dalrymple, The Knife Went In

   1 more example

   We aren’t no thin red ’eroes, nor we aren’t no blackguards too, But single men in barricks, most remarkable like you; An’ if sometimes our conduck isn’t all your fancy paints, Why, single men in barricks don’t grow into plaster saints;

   1892, Rudyard Kipling, Tommy