The root of all mental illness is the inability to communicate with either yourself or to others.
With that said, some people stalk others or behave in an unusual fashion which sometimes end with physical violence not because they are sadists, but instead it is because that is how they believe they are communicating with others in a acceptable way and when it is met with rejection it ends in violence as a natural reaction.
As with dolls and other devices, are they really all that bad? I mean aside from being extremely unusual, are they any more different than everything else? I mean sometimes people wish to talk with others. I'm sure many of you as a child either had a tea part or played with dolls of some sort that you talked to. It probably helped develop your social skills and ultimately allowed you to communicate/relate with others. Sort of like talking into the mirror, but instead directing the communication to an object. I had a pet dog as a child and whenever I wanted to talk to someone who would just listen to what I had to say, I would be talking to the dog; and it listens with ears up, and unlike talking with other people you usually end up having someone who listens to what you have to say and perhaps ultimately understands what you're trying to say. It's extremely frustrating to talk with someone, then they talk about something else or avoid your issue altogether. So that is one theory with these dolls: perhaps no one listened to what they had to say so instead they direct it towards an inanimate object that doesn't talk back, change the subject, judge you, or offer unrealistic solutions.
As for sexual relationships with dolls, it is indeed odd. But again it goes right into the whole communication front. Many times men/women cheat on their spouse not because they no longer love the other, but rather sexual desires are not met or at some point certain behavior that is wanted by one is not wanted by the other. I'm guessing some of these men have issues with sex either with their spouse, girlfriend, or others that are not being met and thus, it is channeled in the form of a doll. Is it right or wrong? Who knows.
Ultimately, if you just want someone to talk to, get a dog. If you have sexual desires that are not met, then talk it out with your partner.
Imagine for a moment a world where a doll has the same intelligent as a human. Imagine a world where all your desire, all your wants, needs, and goals are placed in the mind of a doll. Imagine a world where communication is flawlessly executed in the form of interaction with a doll that has the perfect communication skills: it listens, it responds, it understands. Can such a world be created? The endless form of perfect communication between man and machine? Perhaps that is one step these doll makers are trying to achieve. A perfect world. Man's ultimate goal in life is companionship with another. If one can find the perfect companionship, then nothing else matters. Adam and Eve, so to speak, a perfect being, in a perfect world; one understands the other, and the other understands the one. Perfect harmony.
An interesting film to watch would be Twilight Zone's episode about the Electric Sheep(A perfect mother, a perfect person). A good book to read would be Do Androids Dream the Electric Sheep(What is the value of human life?).