The word "fiat" means a decree or a dictate thus indicating a central authority. This does obviously not apply to Bitcoin or bitcoins and we should thus, in my opinion, avoid linking the word "fiat" with bitcoins.
No, I will not avoid "linking" the word fiat with Bitcoin because that is what Bitcoin or any other currency that has no intrinsic value is. Fiat. You may not like that and even choose only the definitions that support your position, but it is what it is. Fiat.
http://goo.gl/fQX918
And he is using the definition from wikipedia's "Fiat Money" page. I'm not saying I agree with him, but he already linked to his definition, so linking to a conflicting definition won't get you anywhere.