As he mentions, Hillary Clinton knew this truth. He mentions that this got her in trouble with the media. It went beyond getting her in trouble with the media.
A death threat on Chelsea Clinton (the daughter) was given to Bill Clinton if information were to be revealed via the Clintons at the Democratic convention about Obama, which information would have given the nomination in 2008 to Hillary.
That is why this type of information was not brought up, and why Obama was nominated by the Democrats in 2008 to be the Democratic candidate, and not Hillary. They remained silent because of the death threat.
That information is in the second video below the video immediately below.