Because once it is out there people repeat it as fact and then ask those who disbelieve it to "disprove it".
The days of letting people lie about you and meekly taking it are over.
And that is a good thing even if you do not approve.
If things went as they did in Russia Russia Russia-Gate, a criminal complaint would be initiated because there were media reports (based on nothing but Perkins Coie lawyers suborning perjury - a crime for which they have not yet been held to account).