Irrational skeptics look and sound much like rational skeptics, but they are spiritually akin to scamsters hype merchants, con-artistes and grifters. The dangers of the latter are rightly well established, the dangers of the former less well so, but they can have also have serious consequences for those who are genuinely and unambiguously interested in the search of truth.
Rational skeptics are by nature conservative, they require substantive proof that something works before accepting it. But, they have no agenda. They will be patient in examining something before dismissing it. If a method does pass rigorous analysis, they will take it on board and incorporate it into the broad body of mainstream accepted knowledge. They are the heroes of science and discovery.
By contrast, proving something to an irrational skeptic is almost impossible. They use a number of tricks which are essentially hostile to the critical analysis. In particular, they generally comment on matters they have no practical experience of. The motivation of the irrational skeptic is ego gratification rather than the search for truth (see point 4).
Here are some of the main tricks you should look out for. I admit I do not know them all, I just know a couple of hundred.
1) I think method A is absurd. Therefore it is absurd. Therefore I do not need to examine it.
2) Advocate of method A promotes a method I think is absurd, therefore he is absurd. Because promoter of method A is absurd, his method must be absurd. (Blur Circular Logic)
3) I do not need to attain practical experience of circumstances in which method A may be employed, because method A is absurd.
4) We should not consider the possibility that method A actually works, because it may harm the naive (Of course, irrational skeptics actually preach almost exclusively to the converted, to buy easy credibility. You will never find an irrational skeptic trying to talk a mark out of parting with their life-savings on some scam. What is the point? Who of the intellectual elite would know?)
5) If it is proven that method A is not absurd, to the extent that I no longer pretend otherwise without losing credibility (the Achilles heel among irrational skeptics), then I will say:
a) The method is unworkable under most practical circumstances.
b) The method is difficult for an ordinary person to exploit.
c) The potential gain or benefit is small for the effort expended.
Note: the above can be applied to almost anything. A strong case can be made for saying that b-c apply to many methods that are scientifically valid, for example. Because the definitions a-c are conveniently vague, the irrational skeptic can imply the practical value of method A is close to zero, whatever its actual value. Its impossible for an advantage play method to exist which does not meet one of these criteria, since it would be corrected by the market if one these factors did not apply.
6) Generally speaking, I will misquote advocate of method A, because I have not examined his sources properly, or because I wish to misrepresent the opinions of the advocate of method A. Once those perverted opinions are established in the public mind as fact, then debunking method A becomes simple.
7) Look at me.
8) I possess the superficial trappings of, though not the substance, of academia, therefore you should respect what I say. Because you respect what I say, accept that method A is invalid.
9) You should respect my opinion on the non-viability of method B, because I successfully debunked method A, etc etc ad infinitum.
The ultimate consequence of the behaviour of the irrational skeptic is a general dampening of progress in the field of knowledge, which has serious consequences for all of society.