"But you can't expect people to act rationally. We are emotional creatures."

This may be difficult to answer appropriately without knowing what the hypothetical speaker means with “emotions” (or "expect", for that matter). But the phrase seems to me like a potential cached one, so ve may not know it either.

A possible elevator response below:

Rationality is not Vulcan-like behavior; you don't have to renounce to your emotions in order to act rationally. Indeed, for most people, many emotions (like affection, wonder, or love) are very valuable, and applied rationality is knowing how to obtain and protect what is truly precious for you.
What is important is to rationally understand how your emotions affect your judgment, so you can try to consciously avoid or damper unwanted emotional reactions that would otherwise have undesirable consequences for you.