plaster saint 
noun
A person who makes a show of being without moral faults or human weakness, especially in a hypocritical way: she is no plaster saint—she acknowledges her faults and is quick to ask forgiveness...
- We were all trying to be as solicitous of her family as we possibly could, without making her a plaster saint, which is not very realistic.
- This is absurd, of course, but it is also unfair to Washington, who is less of a plaster saint and therefore more interesting than his biographer makes him out to be.
- He's no plaster saint (like the rest of us).