Flag Protection Act of 2004 - Amends the Federal criminal code to revise provisions regarding desecration of the flag to prohibit: (1) destroying or damaging a U.S. flag with the primary purpose and intent to incite or produce imminent violence or a breach of the peace; or (2) stealing or knowingly converting the use of a U.S. flag either belonging to the United States or on lands reserved for the United States and intentionally destroying or damaging that flag.