So yes, indeed, real people with malicious intent can and will monologue to those they have in their power

From Villainous Monologues: They May Be More Common than You Think by Caroline Furlong.  

One of the oft-mocked tropes in fiction is the Villain’s Monologue. For example, in a story the villain will somehow manage to capture the hero and hold him at his mercy on the train tracks or in his scientific lab. Then, rather than get on with the murder or the torture, the villain chooses to make a grand speech. Sometimes this speech ends with him murdering or hurting the hero, but just as often it ends with either the heroes’ friends showing up to rescue him or the hero figuring out how to get free on his own.

Critics and some audiences scoff at this. “How could anyone be so stupid?” they say. “Do the writers think real people would monologue like this rather than act quickly and decisively?”

Writers do not think real people would do this. Rather, writers know real people have done this and continue to do it because some people really believe they are the center of the universe and everyone should bow down to worship them – and that if they do not bow and worship, then they should be punished for ignoring the Great Center of All That Is. You can easily look up this mental disorder: it is called narcissism. Many people have had it and still do.

It is not hard to look up long-winded speeches from genuine historical villains. Hitler liked to hear himself talk. So did Stalin and Mao. Lenin wasn’t any different. So yes, indeed, real people with malicious intent can and will monologue to those they have in their power – or those whom they believe they have in their power.

I have always considered people who wish to monopolize a conversation to simply be selfish boors who like the sound of their own voice.  Indeed, a narcissist.  (Discounting those conversations where there is an asymmetry of knowledge or utility.)  

Furlong introduces the mirror interpretation which is certainly also valid.  There are conversational monopolists who do indeed love the sound of their own voice.  But there are also those occasions where the monopolist either dislikes the voices of their conversational partners or discounts their value.  

It is a refutation of Classical Liberalism in which all humans are accorded the same natural rights and understood to each be unique life stories.  There is always something to be learned from someone else, though it might take some digging to unearth it.

For the monopolist though, there is a hierarchy of value and some people simply don't make the cut.  They are not considered to be unique individuals but much of a muchness.  They have nothing to offer except their attention of adulation of the conversational monopolist.  

Are they necessarily evil?  I am not so sure.  Perhaps predisposed to evil though.

There are two forms of the conversational monopolist.  The one who breaches good manners because of their selfishness and self-love.  The other is described by Furlong, those who demonstrate bad values by their disregard for the individualism and equality of natural rights of others.