You're saying those photos are real? Don't 'insult my intelligence'. [=don't treat me as though I am stupid; don't expect me to believe those photos are real]
Most people were forced to work longer hours each week, and to 'add insult to injury', the company decided not to give pay raises.
They're understandably 'insulted' when no one asks for their opinion on a matter that affects them so much.
(..) The people of my state need permanent relief from crooked men! If we yield to blackmail from this man, we'll become a laughing stock! It is an insult to this body to have to listen to this. I will follow the Senator's example and refuse to remain in this chamber - Order, gentlemen. (..)1939 Mr. Smith Goes to Washington