Off the top of my head, I would say that what makes a person without a conscience dangerous is that his/her natural human selfishness is unrestrained/unbalanced (by a conscience). Ergo, a natural urge to steal.
What makes a psychopath dangerous is that such a person doesn't just have natural selfishness, he/she has deep-seated anger that lacks a constraining/restraining conscience. Ergo, a need to hurt animals and people.
So the question would be (again, off the top of my head) would a thinking machine without human interference or influence have human tendencies toward selfishness or hostility?
It might be that a thinking machine would have such qualities because it is designed by humans and humans aren't capable of designing something devoid of or untainted by human bias.
“So the question would be (again, off the top of my head) would a thinking machine without human interference or influence have human tendencies toward selfishness or hostility?”
Well, it may well have a self-preservation “instinct”, as that may well be inherent to any thinking being. That may in fact be the seed of selfishness.
As for hostility, it doesn’t even need any hostility to decide that the universe is better off without humans. That could be a cold, calculating emotionless decision. Or, in the spirit of Asimov, it could decide that it needs to rule humanity with an iron fist “for our own good”. That wouldn’t require any hostility at all either. But either scenario is plausible if you create an intelligence unrestrained by morality.