The standard NPC response to the Hunter Biden revelations is simply to deny their veracity by attacking the source. "Guliani is part of the Trump crime family" or "The New York Post is a tabloid rag owned by Murdock," or the classic, "this information was really obtained from Russia."
Don't fall for the trap of arguing with the NPC over this issue. It's a way for them to keep the observer's mind off of the full ramifications of these revelations. They would love nothing more than to keep the focus on Giuliani and the New York Post and Russia Russia Russia. Even if they lose the argument they've won a strategic victory.
Instead ask them "what if it's true? Would you still support Biden?" Ask them if they can justify it and make them give a justification. Then ignore their deflections and point out the consequences of what it means if it's true,and ask them again if they would still support Biden if the information was verified.
After you've hammered out the consequences it made it clear to them and all third parties what these revelations mean, then you can talk about their veracity. But do not start there.
In my experience you have to use their own tactics against them. Shame them for their blatant stupidity.
"So Russia somehow faked the pictures of Hunter Biden smoking crack with hookers, even though he knocked up a stripper/hooker already? If that was the case why didn't the Biden campaign call them fake instead of a 'hack'? That is like some flat earth level conspiracy shit right there if you still believe muh Russia."