Most people are afraid of machine sentience because they have NO IDEA about how computers work.

After I took my first electrical engineering course, it became painfully obvious to me that computers would never gain sentience. Computers are only capable of performing calculations on preexisting data. Sentience requires originality, and computers cannot create original ideas.

And, even if computers one day become self aware, I fail to see why malevolence should be considered their default personality trait. But that kind of thinking doesn't sell movie tickets, so...whatever.