If he knows your lying your most likely mafia, the chances of you being a power role are 33% (for the mafia side) wouldn't he want to sit quietly while the others kill eachother slowly?
Not at all. The Reporter needs to survive.
If he reveals himself, no one would kill him, since that wouldn't advance the board for either side.
If he shows someone didn't do an action, Town would investigate someone different and end up increasing the chance to kill the Mafia Doctor and the Serial Killer - and Mafia would kill a different person (who is a Vanilla or the Vigilante), which would also increase the chances of killing a Power Role.
If he shows someone did an action, Mafia would try to kill this person if he is not part of the Mafia.
Either way, he can make a greater wreck if he reveals himself and his results.
Elevation - The Rise of the Mercenary
Show me the gold and I'll show you victory.