The cardinal judged MC from his knowledge and what she did to see if she is going to harm him or his g**. This is also what makes MC so annoyed that she thought the "egotistical person" would suit him. However, he lived under the curse and mockery of the other cardinals calling him names and stuff. Egotistic is probably just one of them, so he thinks she was just mocking him like any other person, whereas he still considered that advice and he believed she didn't have any bad intentions. That is when he repaid her with a hint.