those kinds of stupid lies may work on brainwashed russians in ryazan glued to rossiya-1, but anyone at least only barely coherent considers such "news" to be as valid as the "news" of ukrainian werewolf supersoldier biolabs

in other words, don't worry about stupid russian lies

russia's power is on the decline

I would simply say: "As an astronomer, I would like to say this so called paper is a waste of your time, here are the top 3 problems with it...". And then give him a short list of the worst ideas in the paper with rebuttals.

Put it another way: it's worth debunking, but not worth spending too much time on it.

I voted to answer and debunk, but briefly and dismissively to be clear it's not worth anyone's time.

Normally I am against engaging deniers of any kind (I was a Green Party candidate a couple of times, so...), but this is different. You're not confronting the delusional person and/or professional liar, you have the airtime and audience to yourself.

(It's a fool's errand to debate people who are brilliant liars. They will 'win,' every time.)

I’m not familiar with the paper you reference, although I did read some of his book on ‘Oumuamua’. I’m not a scientist by any definition, however I thought he made some potentially valid points.

I am uncomfortable with the scorn he receives. Just because it’s far out doesn’t make it untrue. History is teeming with examples where someone came up with a theory that was rejected by the scientific establishment, and later proved to be true.

Debunk, but with evidence.

that paper abstract is hella primed for media science correspondents to pick up and run with it. There's incitement of dread (mentioning Dark Forest), appeal to paranoia ("what if it does covert things behind the Sun where we can't see it!"), and pressuring sense of urgency ("autumn this year!"). This absolutely needs someone to splash cold water on it before it's released into the news cycle unopposed.

I think the best thing you COULD do is say something like "they're jumping to conclusions based on faulty assumptions" or talk about the selection bias inherent in how they appear to have massaged statistics to make it sound like it's maneuvering unnaturally. I dunno how rigorous their orbital mechanics methodology is, but I do know there's nothing necessarily unusual about an object entering the solar system in retrograde.

He thinks this thing that was spotted two weeks ago is aliens. He always says it's aliens. He has never said anything other than "it's aliens".

At this stage, the battle shouldn't be debunking the individual claims but getting the press to understand and recognise the con.