Where do journal editors look to find someone to referee your manuscript (in the typical “double blind” review system in academic journals)? One obvious place to look is the reference list in your paper. After all, if you’ve cited them, they must know about the topic of your paper, putting them in a good position to write a useful review. The problem is that if your paper is on a topic of ardent disagreement, and you argue in favor of one side of the debates, then your reference list is likely to include those with actual or perceived conflicts of interest. After all, if someone has a strong standpoint on an issue of some controversy, and a strong interest in persuading others to accept their side, it creates an intellectual conflict of interest, if that person has power to uphold that view. Since your referee is in a position of significant power to do just that, it follows that they have a conflict of interest (COI). A lot of attention is paid to author’s conflicts of interest, but little into intellectual or ideological conflicts of interests of reviewers. At most, the concern is with the reviewer having special reasons to favor the author, usually thought to be indicated by having been a previous co-author. We’ve been talking about journal editors conflicts of interest as of late (e.g., with Mark Burgman’s presentation at the last Phil Stat Forum) and this brings to mind another one.
But is it true that just because a reviewer is put in a position of competing interests (staunchly believing in a position opposed to yours, while under an obligation to provide a fair and unbiased review) that their fairness in executing the latter is compromised? I surmise that your answer to this question will depend on which of two scenarios you imagine yourself in: In the first, you imagine yourself reviewing a paper that argues in favor of a position that you oppose. In the second, you imagine that your paper, which argues in favor of a view, has been sent to a reviewer with a vested interest in opposing that view.
In other words, if the paper argues in favor of a position, call it position X, and you oppose X, I’m guessing you imagine you’d have no trouble giving fair and constructive assessments of arguments in favor of X. You would not dismiss arguments in favor of X, just because you sincerely oppose X. You’d give solid reasons. You’d be much more likely to question if a reviewer, staunchly opposed to position X, will be an unbiased reviewer of your paper in favor of X. I’m not biased, but they are.
I think the truth is that reviewers with a strong standpoint on a controversial issue, are likely to have an intellectual conflict of interest in reviewing a paper in favor of a position they oppose. Recall that it suffices, according to standard definitions of an individual having a COI, that reasonable grounds exist to question whether their judgments and decisions can be unbiased. (For example, investment advisors avoid recommending stocks they themselves own, to avoid a conflict of interest.) If this is correct, does it follow that opponents of a contentious issue should not serve as reviewers of papers that take an opposite stance? I say no because an author can learn a lot from a biased review about how to present their argument in the strongest possible terms, and how to zero in on the misunderstandings and confusions underlying objections to the view. Authors will almost surely not persuade such a reviewer by means of a revised paper, but they will be in possession of an argument that may enable them to persuade others.
A reviewer who deeply opposes position X will indeed, almost certainly, raise criticisms of a paper that favors X, but it does not follow that they are not objective or valid criticisms. Nevertheless, if all the reviewers come from this group, the result is still an unbalanced and unfair assessment, especially in that–objective or not–the critical assessment is more likely to accentuate the negative. If the position X happens to be currently unpopular, and opposing X the “received” position extolled by leaders of associations, journals, and institutions, then restricting reviewers to those opposed to X would obstruct intellectual progress. Progress comes from challenging the status quo and the tendency of people to groupthink and to jump on the bandwagon endorsed by many influential thought leaders of the day. Thus it would make sense for authors to have an opportunity to point out ahead of time to journal editors–who might not be aware of the particular controversy–the subset of references with a vested intellectual interest against the view for which they are arguing. If the paper is nevertheless sent to those reviewers, a judicious journal editor should weigh very heavily the author’s retorts and rejoinders. 
Here’s an example from outside of academia–the origins of the Coronavirus. The president of an organization that is directly involved with and heavily supported by funds for experimenting on coronaviruses, Peter Daszak, has a vested interest in blocking hypotheses of lab leaks or lab errors. Such hypotheses, if accepted, would have huge and adverse effects on that research and its regulation. When he is appointed to investigate Coronavirus origins, he has a conflict of interest. See this post.
Molecular biologist, Richard Ebright, one of the scientists to Call for a Full and Unrestricted International Forensic Investigation into the Origins of COVID-19 claims “the fact that the WHO named Daszak as a member of its mission, and the fact that the WHO retained Daszak as a member of its mission after being informed of his conflicts of interest, make it clear that the WHO study cannot be considered a credible, independent investigation.” (LINK) If all the reviewers of a paper in support of a lab association come from team Daszak, the paper is scarcely being given a fair shake.
Do you agree? Share your thoughts in the comments.
 The problem is compounded by the fact that today there are more journal submissions than ever, and with the difficulty in getting volunteers, there’s pressure on the journal editor not to dismiss the views of referees. My guess is that anonymity doesn’t play a big role most of the time.