Saying that is an alien probe it's not an argument, just an untested hypothesis. What follows on the paragraph is an argument, albeit a bad one.
This is nonsense. Every claim has an corresponding claim of its negation. Which one has the burden of proof?
What evidence do you have that it's an asteroid?
The burden of proof is on the latter, this is just SoP in science. Otherwise we end up with a world full of superstition, as it was for most human history.
We have no evidence yet of other intelligent life in the universe. But we know there are quadrillions of asteroids all over the place, some of which pass by us every so often.
Occam's razor, correctly stated, says that, all else equal, the explanation that relies on the fewest assumptions is most likely the true one. Given our lack of evidence for intelligent life, and preponderance of evidence of asteroids, the former explanation requires far more assumptions than the latter.
It is also not a comet, so the null hypothesis is that it’s a rocky natural object but it doesn’t mean it’s an asteroid.
The best classification we might have for it is a distant detached object (DDO) but since it’s likely not part of our solar system it can’t be classified as a detached object by the current minor planetary object classification system we have either.
In most cases the "claim of negation" is the default position (related to the null hypothesis). If I claim there are invisible faeries that hold us to the earth. The negation of that claim is that there aren't. But this sort of reasoning only applies to things like debate and philosophy.
Science is fine with the unknown, claims must meet the burden of proof to be considered more than a speculation. Hence a "claim of negation" isn't scientific, because you instead present observation and calculation which makes the claim invalid in the first place. The default state being that no claim (we call these hypothesis) is valid. Sometimes this means that there are many competing partially valid hypothesis. One can't prove a negative, so instead science deals in hypothesis and only ever judges the positive claim against what we know. I can't emphasize this enough, there is no such thing as a negative claim in science: just a claim that we don't know the answer yet because no current hypothesis are convincingly valid.
People aren't claiming it's an asteroid, because that has a specific definition it doesn't match. Note in the article he talks about comets as one thing some people think it is. In the title of the article it's "Interstellar Object" which I don't think anyone is disputing.
The hypothesis he is putting forward is reasonable though. At least as well as any other hypothesis. We don't really have proof (observations) either way (and like a good scientist he spends a lot of time pointing out how we should be ready next time) so no hypothesis can meet a burden of proof at the moment. But then science doesn't really use a concept of "burden of proof", that's a legal concept. Instead we simply work with our least wrong models - even our best theories are not proven - which are judged by how well they predict the world.
And in this example the hypothesis "aliens did it" answers a lot of questions in a reasonable way. But then so does "nature did it" but some of the answers and mechanisms are less convincing in that case. And I think the point the interviewee is making is that we should be ready to better answer that question next time an object like this comes by because the answer "nature did it" is somewhat unconvincing for this object.
Suppose I show you a jar containing a large number of coins and I claim the number of coins is even by just looking at the jar. Do you have evidence that I am correct? No! Just by looking at it I can't possibly know the exact number of coins. But this means that the logical negation of my claim is true ( the number of coins is odd?). Also no! Again, I can't know the exact number of coins by just looking at it.
So although there are only two possibilities, I have no evidence at all. And this means the only claim I can make is the null hypothesis: I don't know.
Absence of evidence is not, itself, an evidence of absence. In other words, if I don't have evidence that you committed a murder, it doesn't mean you're innocent. It means just that: I don't have evidence to convict you, and I must dismiss the case.
Secondly, science doesn't prove. It creates models, and finds the ones that stand up to close scrutiny. Bretz provided massive evidence for his flood model. Those who chose to ignore him chose to ignore the evidence ... whatever their names were.
The one making ANY claim has the burden of proof. The null hypothesis is the default whenever there's no evidence supporting any claim. It is basically a fancy way of saying we don't know what it is.
It's much more likely that it's ejecta from some event from outside our solar system. Or a redirected Oort body.