Corporations cannot plead the 5th. That only applies to individuals. And it only applies when there is any reason to believe there is a risk of self-incrimination.

So yes, if you are in a circumstance where pleading the 5th is allowed, then you may plead the 5th and therefore not comment. But in the case of a corporation, or in the case of circumstances where you may not plead the 5th, then you cannot escape punishment by asserting that you are in a catch-22.

As Mitt Romney was fond of saying, "corporations are people"

Sure, and legally in many ways corporations are people. But in this specific case, corporations do not enjoy the protections of the 5th amendment.

[Citation needed]

I learned it from The Illustrated Guide to Law, which is a webcomic about law written and illustrated by a criminal defense lawyer.

The page that states this is http://lawcomic.net/guide/?p=2600, though the next couple of pages are relevant as well.

This only works if your testimony is the only evidence of the crime.