Why do people think IPs lie?

This person that has been stalking me tried to use many IDs at once to basically act stupid. What she didn't realize was that the IP was exactly the same. Why don't they listen when you tell them flat out you know it's them because of their IP? I think it's a little coincidental that all of those people are acting stupid living on one street. And how do they turn Ignore off? What's wrong with these people? And why be so cowardly as to allow communications temporarily in order to send mail but too much of an infant to receive it? Anyway, same IP to me means same person. What's your take on it? BTW, I used IP tracers as well, so I know for a fact they are the same person. Right down to the street they live on.