objective as a pancake

very objective. (*Also: as ~.) A simile used to describe a high degree of objectivity and reasonableness in the assessment of a product, idea or statement that is neither influenced nor affected by personal feelings or opinions in considering and representing facts.

"This is an incredible report!", Andres exclaimed, holding Lily's completed report on Sub-atomic Quantum Physics in his hand. "You're just saying that to make me feel better," Lily replied, sighing. "What're you talking about? I'm being as objective as a pancake. Seriously," Andres replied.