Answer:
They provide false reasons in support of a claim, making the writer seem less credible.
Step-by-step explanation:
The use of fallacy is using faulty arguments to support the opinion. At the first glance, the fallacious opinion can seem better than it is, but it is not supported by facts, and the reader can have the feeling the writer is dishonest.
By using fallacies, the writer is discrediting his work and words.