Did you know that whether someone is under oath or not it is a crime to lie to the FBI?
Like when Hillary was interviewed by the FBI. She wasn't under oath. So she lied to the FBI (and wasn't charged for it), or she told the truth to the FBI (and wasn't charged for it).
So if there's no evidence of collusion, Trump can go and tell the truth and he won't be in the same position as Hillary -- who committed a crime either way. But, hey, it's okay to leave her alone because she apologized, right?