In a functional requirements document, is the Assumptions section dangerous?

Question

I am currently a reviewer on a Best Practices document for Developers or Business Analysts in writing a Functional Requirements document. This document is not necessarily a template for functional requirements documents, but a guide to what elements are necessary, optional, and dangerous to include a Functional Requirements document.

The author of the document states that:

Functional Requirements documents should NEVER have an Assumptions section! Do not assume anything about what people know about this application or any external issues surrounding it.

I am not sure that I agree with this sentiment but don't really have the words to refute it either. In a perfect world the analyst will have time to properly analyze every stakeholder input and every possible external issue but inevitably due to time constraints and other issues some assumptions need to be made.

Is this a bad idea because it is too easy for the intellectually lazy to declare assumptions rather than requirements? If not then why do you think Assumptions are a good idea?

EDIT: To clarify, I am not asking about the Assumptions section of technical documentation but of an Assumptions section in a requirements document written by a non-technical business analyst.