Since I can't seem to convince you, here's a definition of "Derivative Work" straight from 17 U.S.C. 101 (https://www.law.cornell.edu/uscode/text/17/101) (emphasis mine). (FWIW, I am a licensed attorney who specialized in IP law while in law school; this is not legal advice.)

"A “derivative work” is a work _based upon one or more preexisting works_, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, _art reproduction_, abridgment, condensation, or _any other form in which a work may be recast, transformed, or adapted_. ..."

As applied to the company logo in question, the language is pretty well on point. I'd tread with caution unless the company has made it clear they approve of the work.

I don't consider the Facebook logo itself to embody a level of unique creative expression sufficient to qualify as an artwork. Obviously, if contested, that decision could be overruled by a judge, but I like my chances there.

  .-----.
  |   .-|  Probably does not
  |  -+-|  violate copyright.
  |   | |
  '-----'

The bar for qualification as an artistic expression is extremely low. See _Feist Publications, Inc., v. Rural Telephone Service Co_, 499 U.S. 340 ("To be sure, the requisite level of creativity is extremely low; even a slight amount will suffice. The vast majority of works make the grade quite easily, as they possess some creative spark, "no matter how crude, humble or obvious" it might be.")

You'd be better off arguing some other angle, but please study law first so as not to waste anyone's time.

...as though only the opinions of lawyers count when it comes to the laws that govern everybody. This is why right to trial by petit jury and indictment by grand jury are written into the federal constitution and most state constitutions. The purpose of studying law is so that justice may exist in a society that has abandoned the use of force as the first means of resolving disputes. It is not to shut down a debate via appeal to authority.

What's wasting everyone's time is the rich and powerful trying to mine out and own every last corner of culture. I'll be damned if I will allow Facebook to own every blue square with a lowercase 'f' in it, rather than just the one they use to mark their service. You may feel otherwise, but until this matter actually goes to trial, that's just, like, your opinion, man.