You can't mean that!

You can't mean that!

I refuse to believe that you earnestly believe or intend what you said! A: "I'm sorry, Bill, but we're going to have to repossess the house." B: "You can't mean that! My family has been in this house for six generations!" A: "I think we should see other people." B: "No, you can't mean that! I thought you loved me!"
See also: mean
Farlex Dictionary of Idioms.

You can't mean that!

Inf. Surely you do not mean what you said! Bill: I hate you! Mary: You can't mean that. Sally: The cake burned and there's no time to start another before the party. Mary: You can't mean that!
See also: mean
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • I do believe
  • believe (one's) ears
  • believe ears
  • believe one's ears
  • so (something) it isn't true
  • so bad, stupid, etc. it isn't true
  • have the gall to (do something)
  • have the gall to do
  • don't you believe it
  • don't you believe it!