"...I have to retrace my steps by way of the shadows. I try to interfere as little as possible in the evolution of the work. I do not want it to be distorted by my opinions, which are the most trivial things about us." (Jorge Luis Borges)
In your scholarly writing, there is no way around forming an opinion. I know the temptation to think of our opinions as "trivial" and the desire to write a text that is not "distorted" by them. (Such a text is a poem, which is "the work" that Borges is talking about.) I know academics who find opinions tiresome, and who would like their writing to be about something else. But I think they have somehow gotten into the wrong line of work. Opinions (claims, propositions) are absolutely central to the scholarly enterprise.
Scholars should deal in more than "mere" opinion of course. They should be able to defend their opinions, to engage in "discourse" about them. Their confidence is not mere arrogance, their resolve is not mere stubbornness. When they make claims they are expressing opinions that are well founded in reasons to hold those views. When you talk to them, when you push back against the claims they make, you encounter the resistance that those reasons provide. The art of writing a prose paragraph, the art of academic writing more generally, is the art of making those reasons explicit. When scholars communicate in writing, they are telling each other what they believe and providing each other with reasons for those beliefs.
As a young scholar, or even a student, you therefore do well to examine your opinions in a systematic way. The "spiritual exercises" that I've been talking about his week offer such a system. In fact, you might recall that not long ago I presented a utopian vision in which undergraduates give themselves 640 occasions during the course of their studies to examine their opinions. Such students will develop disciplined minds and they'll become more articulate people.
Over at OrgTheory, Fabio Rojas recently posted a TEDx Talk about irrationality in politics by Michael Huemer. He rightly reminds us that it's somewhat inconvenient to be rational because it means that you can't believe anything you want. If you're rational you have to have reasons to believe. It's not about merely being "opinionated", its about being able to make explicit the reasons you have for holding your beliefs.
I suppose it's the difference, also, between being a "moralist" and actually being a moral person. Those who engage in orderly self-examination on a regular basis will have a number of moral attitudes that guide their behavior. They will also be less able to denounce the actions of others in a superficial way. They know that their opinions about behavior apply only in particular circumstances and that we really only know in our own case whether those circumstances obtain in any given situation.
Academic writing is the orderly formation of opinions in prose. A process of making claims and supporting them with arguments. That's why academic discourse is the way it is. Like I always say, it's not for everyone. But it does serve a particular social function.