What is there to agree or disagree with here?

@Darth_Algar: Well, for example that those who believe in ETs are not convinced sooner or later.

So, you’re asking whether we believe in aliens or not?

I take it that the part we are supposed to agree or disagree with is Mulder’s claim that “all the evidence to the contrary is not entirely dissuasive.” In other words, we are being asked whether or not we agree that that the evidence against there being extraterrestrial life on Earth is dissuasive. Alternatively, the question might be whether or not we believe that there are extraterrestrial lifeforms currently on Earth (which is a similar, but slightly different, question). Presumably, we are also being asked to think specifically about sapient extraterrestrial life (as opposed to, for example, some microbial stowaways from a meteorite).

As much as I enjoyed The X-Files, however, I don’t think that sapient extraterrestrial life is currently on Earth. There is almost certainly life elsewhere in the universe, and the likelihood that there have been other sapient creatures in some place and at some time in the vast expanse and history of the universe is pretty high. But the mere existence of sapient alien lifeforms somewhere and at some time doesn’t give us any reason to believe that any of them have made it to this planet at this time.

But is the evidence to the contrary entirely dissuasive? I suppose that depends on the person considering it. Plenty of people are convinced that there are aliens currently inhabiting the Earth, and some of them are intelligent and highly educated on the subject. Insofar as it’s not just crazy conspiracy theorists with nothing more than a hunch who believe there are aliens among us, I suppose we can’t say that the evidence is dissuasive enough to convince all rational and reasonably intelligent people.

Isn’t it just saying ” I don’t know?”
In other words it could be or not be possible?
No one knows for sure , its saying until proof of it comes to light.