Is Othering negative?
It seems to me that Othering is almost always a negative thing; you're denying the subjectivity of someone(s), claiming to know all you need to know about that person(s) by using whatever discerning criteria you decide is significant. Whether those are the dominant significant criteria of Euro-American culture (the rational adult European male is the banal normative individual) or some other cosmology, Othering presumes a static identity, static relationships (usually hierarchical), and precludes the possibility of change of the aforementioned significant criteria over time. In short, Othering objectifies. If anarchists are interested in a flowering of relationships that skirt, transcend, and/or destroy those based on power, hierarchy, domination, and exploitation... if we are interested in creating a culture of masters without slaves... then Othering should probably not be part of our interpersonal practice.
Do anarchists Otherize capitalists (and presumably other so-called enemies)?
Probably far too often. Probably the only worthwhile insight of Hegel was his radical notion that slavery damages the master as well as the slave. We can update and perhaps understand this insight by saying that patriarchy damages men, white supremacy damages white people, and capitalism damages capitalists. This is not a moral exercise; I'm not saying that we should pity the poor white male capitalist -- he's doing just fine, thank you. But to deny that systems of privilege do not harm the privileged is untenable. Again, I'm merely being descriptive. Nobody should feel sorry for those assholes.
Perhaps the question behind your question is along the lines of "Is it strategically wise to Otherize our enemies come the Revolution?" Or something like that. There are some anarchists who, like Marxists, revel in class revenge fantasies. They hold that on the Day After the Revolution, we can start to clean up all the shit that was holding us down. And naturally that includes individual capitalists, politicians, cops, judges, prison guards, etc... A few well-placed bullets are supposed to solve a lot of problems, AND help keep the forces of reaction at bay... So the story goes.
But the issue is clouded by what is sure to be a large part of the non- or small-time exploiting population who will just want things to settle down so they can take care of their needs with other more or less normal folks -- not counter-revolutionaries. If we believe that The Revolution is some Transformational Event (or series of Events) that has the power to alter previously apathetic and exploited people into self-conscious revolutionaries, then we must necessarily believe that transformation is possible for everyone, even those we previously deemed enemies. If we do not or cannot accept such a possibility, what makes us different from Inquisitors and Chekists? The execution of ten or ten thousand alleged counter-revolutionaries was not the tipping point that prevented the full implementation of Marxism in every place where its ideologues attained state power.
Can you identify an enemy without Otherizing?
Naturally that all depends what you mean by "enemy." I think it's possible to find someone's philosophy so objectionable, their social practice so noxious, their interactions with you so damaging that it would be reasonable to say "that person is my enemy." To do so without dehumanizing her_him is tricky, because as the focus of hatred, it's far simpler to deny her_him equal consideration -- especially if that person has access to systems and institutions of domination and exploitation. Your question brings up another question for me: "What is it we are supposed to do once we declare some person(s) my/our enemy?" Can we separate an enemy from the institutions s_he is a part of? Should we try? Are we interested in collective guilt and guilt by association?
These are spontaneous and provisional thoughts that come to mind by looking at what is a very heavy and provocative (in the good sense) set of questions.