Review, critique, opinion, literary analysis—what’s the difference and who cares, it could be asked. The question itself does a good job of pointing out part of the problem. One of those things, to quote a Sesame Street skit from my youth, is not like the others; one of those things does not belong. Opinions are fine things to have, in whatever style or quantity they come. But despite a disturbing trend in some quarters to treat them otherwise, opinions are not the same as facts. They can not and should not carry the same weight.
It can admittedly be difficult on occasion to sort out the reasons why this is so. Certainly a strong opinion is probably at the root of most critical analysis, as what motivated the examination in the first place. But opinions are free from the necessity of being fact-based, whereas review and critique are not. Opinions are tricky as well, because they often feel so right. They may very well be so—fact-based opinions are part of the species—but the problem arises when they are not, and yet are treated as though they are.
This is what leads to the “self-bias” of the title. “Self-knowledge is the key” can be seen as the flip side of “write what you know.” There needs to be a reality check, though, if you are going to present your thoughts as anything describing the factual world. Review is essentially summary colored by preference. Critique implies some comparison with similar or different items of kind. Literary analysis should dig even deeper, examining the context of the piece in addition to the summary and comparison mentioned. Any of these can be illustrated by opinion, but they are failing to meet the requirements of intellectual rigor should they rely primarily on anecdotal evidence.
It is impossible to be completely unbiased, true, despite the degree of rigor. As I said, the opinion often resides at the foundation of the theory. The remedy is to be up-front and clear about known biases, or any suspected others. This gives the reader some means of measurement linking what is being presented as fact with the concrete world. It has the side benefit of providing a tone of honesty by virtue of its openness, as well.
Then again, why take my word for it? An editorial is, after all, only an opinion.