Would being mean to the stalker stop them from coming around? Personally I like LaBlue0314's approach; give them a gift and be nice. I suppose in the DU expansion that's programmed in.
In my game early on with no expansions, had a guy that kept coming around to Teresa Calhouni, (my starting character). I did have her flirting and all that with him early on. But after she hooked up with Don Lothario, it was over. Or it was supposed to be. But he kept coming around. I had Don Lothario go and be mean to him. Finally on autonomy one time he went and punched the guy out. Heh! He never came around while Don was there. But after I moved Don Lothario to a different house, that guy started coming back. So I got Teresa's son Rohber to go out and be mean to him. Rohber isn't athletic at all like Don, but has mischief skills and scared the stalker off. After I moved Rohber out to his own place, the guy started coming back again. I got irritated enough with this and found him in the manage households on manage worlds and deleted him. lol
(I did have Teresa be mean to him too, but he still kept coming around and calling her phone all the time.)
Reminds me of that Ray Stevens song; "It's Me Again Margaret!" :D