To give a serious and long answer, there are two aspects here: law and ethics.
Law: "Farenheit 451" is not trademarkable as a phrase, neither there is a way to copyright it as the title (as opposed to the book itself). The title consists of a name of a person (as well as an allusion to the unit of measurement of temperature) and a number.
I do not see, how one can possibly complain that from the point of view of existing law, Moore is in the wrong.
Ethics Yes, "Farenheight 9/11" clearly alludes to the Bradbury's title. Your question is basically whether it is ethical for Moore to have used the phrase "Farenheight 9/11" without Bradury's permission.
I will say, that it would have been good if Moore had requested one and gotten it. As a courtesy. However, I do not see even an ethical problem with it. My key thought is, where do you draw the line?
Is "
"Celicium 9/11" allowed? How about "
Kelvin 9/11" or ,let us say,
"Newton 9/11"? One can argue that a clear parallel with Bradbury's title exists in each of the cases. More examples: should Bradbury be concerned about people calling their books
"Dandelion salad" or
"Amber Chronicles"? From a completely different area, should
Pink Floyd worry about a band that calls itself
Anderson Council? (in the latter question there
is actually a copyright issue, and btw, the band Anderson Council does exist).
Should George Orwell's estate contact Voinovich about the "Moscow, 2042" title?
What you might see as stealing, I see as an homage. Homage does not require permission from the party that is being homaged.
Now,
>By your logic I will be completely all right naming a children movie >"Garry Dotter".
Two points: (i) isn't there something like this already in existance? Some Russian-language lit about a girl? (ii) I am absolutely sure that the name "Harry Potter", the likeness, and the storylines are copyrighted and the important parts are also trademarked. Call your character "Garry Dotter" in a setting similar to the original and you have lawsuit waiting to happen. But if you have a character named "Garry Dotter" in a situation where you can claim fair use (minor character, parody, homage), you can use the name.
I am sure there exist plenty of books in the world where character names (John Smith, Jack Brown, Ivan Petrov) coincide. There are lots of books, musical albums, songs, movies etc... with similar or identical titles. The world is not going to end because of it.
In his original title, Bradbury has used the name of another person, which also serves as the unit of measurement of temperature. You are
not going to argue that he should have asked permission to use it from the Farenheight estate and from the Chamber of Measures or American Society of Physicists... Are you?