Positive belief bias refers to the tendency to accept more plausible conclusions. As a result, when arguments and conclusions coincide with people's prior ideas, the positive belief bias encourages them to embrace logically defective arguments and incorrect conclusions.
They're skewed, hence they're incorrect!" That is a logical fallacy. (It's known as the bias fallacy.)
One would be arguing ad hominem if they focused on someone's character rather than their argument. So we don't need to break down the overall category of logical error into subcategories to see why the conclusion doesn't always follow from those assertions.
In most circumstances, bias cannot logically invalidate an argument. Bias, on the other hand, can undermine trustworthiness.
In practice, we don't have unlimited resources to evaluate every allegation, so we rely on credibility, which is frequently influenced by prejudice. For example, both the New York Times and Breitbart are prejudiced, but Breitbart is significantly more biased and hence less reliable from a practical standpoint (and of course, they are less credible for other reasons as well).
Due to its prejudice, an overtly biased pro or against marijuana website is unlikely to be a reliable source of marijuana information.
While we cannot logically dismiss an argument because it is biased, excellent critical thinking skills sometimes require us to dismiss a biased source as lacking in trustworthy information, or at the very least to treat it with extra suspicion and seek confirmation from an impartial source.