Don't go down this route. This leads to things like questioning if we can really be 100% super double sure that we landed on the moon, seeing as none of us have any verifiable proof.
Russians were involved in a lot of hacking during the election, and a lot that has surfaced since, like intrusion into power plants, etc.
How do we know this? Because all investigations from the three letter agencies agree on it. Do we have to trust them every time they say they're not spying on us? Or whether they have any active investigations on something? No. But there is no national security or stability reason for them to lie about this. Quite the opposite.
That GP is being downvoted for stating this is disconcerting.