Lot of qualifications here, and an inaccuracy.
“Clearly not interested”? Well, it’s going to be very clear to you, sure, but some people don’t pick on cues (and some people send out mixed cues), or engage in hopeful thinking when it’s slightly unrealistic to keep hope alive–I don;t know how optimism is necessarily “creepy,” even if it doesn’t quite fit with your program or your plans. (To say nothing of “continuing to pester you” for someone who may think, incorrectly, that he’s showing you that he feels strongly about his interest in you, so strongly that he hopes you’ll try a little harder to understand what he’s offering you. To you, of course, he’s offering a pile of lukewarm diarrhea, but not everyone is willing to look at himself from your perspective instantly. He may think he’s a good catch, and wants you to think well of him, too.
But the big problem here is your best case scenario, which is similarly restricting the perspectives to your own: “in all probability, going to be annoying at best”–really? The best thing that could possibly happen is (with your own quaification “in all probability”) is that you’ll be annoyed? How about the perhaps less probable but still possible outcome that you WON’T be annoyed? Ever think of that? That maybe you’ll be charmed? Won over? Change your mind? Guess not, but you expect the guy to instantly go along with your program, and cease and desist because–no woman’s ever changed her mind in the history of the world?