You need to reread your link. Horowitz cleared Holder for participating in the Fast & Furious program. He did not clear him of withholding documents and information from a Congressional Committee that requested it.
The justice department sent the committee more than 7,000 documents relating to Fast and Furious, and to a similar operation that took place during the George W Bush administration.
The Department of Justice said it had denied access to the rest of the files because they contained information that could affect ongoing criminal investigations.
The White House then raised the stakes by announcing it would exert executive privilege to protect the documents in question from subpoena.