There are occasions when some people come on strongly.
To explain, take the following example. Let's say you meet X at a social function either through introductions or just happen to do so somewhere. You have a pleasant conversation because you find that both of you share common interests at some level - movies, music or whatever. And then you exchange numbers and say, yeah, let's meet up sometime. Although really in truth, you in all probability would not bother calling or meeting up unless X is a hot, sexy and horny babe\stud\[whatever] who flirted with you and grabbed your crotch\stuck a finger up your ass\[whatever gets your goat, sicko].
But this time. X calls up next week and asks to meet up. And you're like, uh, really? Wow. Were you that fookin' interesting? But you're busy, really. So you tell him, hey maybe some other time. At this point, the conversation should prepare for ending with the goodbyes and false promises to stay in touch.
But X doesn't get it. He perseveres and says, okay, how about the week after that? I'm good for the week days, blah, blah, blah.
So you check your diary but god damn, for real okay, it's full. Sorry man, you say. I'm full up. Hey, I gotta run, I'll check my diary and get back to you okay?
But X doesn't get it. Okay, how about the week after that one? he asks calm, as a fookin' cucumber, as if he completely missed the bit where you said, Hey I gotta run.
So you reply, Dude/tte/[whatver tf] I said I gotta run, I'll get back to you. Have a nice day.
But X replies and very coolly and calmly almost as if you were the annoying one, Okay, why don't we just fix the date since your diary is open there.
And you're like, what the fook is wrong with this psycho bastard and the shrill violins in Psycho now start kicking up in your head. You now imagine he wants to meet you beause you will be his latest victim. You imagine him spiking your drink and then bundling you back to his place where he saws you off piece by piece. Death claims you soon after he saws off your arm from excessive bleeding. Some of your body parts are incinerated and some are kept in the fridge.
But perhaps you were overdoing it, but his perseverance was becoming annoying if not scary. What the hell you wonder was so interesting about you that X wanted to meet you so badly? It's not like you sucked/fooked/[pon pon] X at any time during the conversation.
So you tell him, I told you X, I gotta run. Bye.
Okay, X replies. You hit the end call button.
You feel relieved. After that stunt, there was no way you were going to meet with him. His coolness was creepy.
Until he calls you again next week. And when you start avoiding X's phonecalls, X diligently leaves voice messages every time to remind you about meeting up with a request to return his\her\[whatever] call over the course of several weeks, with three to four voice messages each week.
Okay, so the point up for discussion is, do you have an obligation to meet up with X after saying in casual conversation that you would? Or to put in another way, could X rely on what you said in casual conversation concerning your interest in meeting up with him? If X could not rely on that statement of interest then what else in that conversation could he or should he not rely on? X may fairly form the opinion that you are a person not to be taken at your word and unreliable.
The dilemma is this: You don't want to take it any further with X but as a parting gift you want to do X a favour. But how do you tell X about this, in the gentlest possible manner, without you sounding like some shitfaced arsehole? I mean to see the X's side would be: how can you without even knowing me, come to the conclusion that I am not worth your time just because I am a little more persistent than others? How dare you be so presumptuous you shitfaced arsehole?
But then why should you give a shit seeing as how you don't want to meet X and X probably (and usually) has no other friends which is why he wants so badly to meet with you after the first conversation? You can't be nice and spend time with everyone, especially those you don't want to or like. Time is your most important asset. You don't want to waste it on people you don't like or don't want to meet.
However that still leaves the question of why you feel X's persistence to be a turn off to be answered. Perhaps it is because X is making immediate demands on your time over the expected measure of time you expected to spend with him. To give an example. You were only psychologically prepared to spend about 5 minutes with X but because of his persistence, it has upset your mental state because the conversation has gone on for 10 minutes. And because of this upset mental state, it has provoked a negative consciousness which X has come to be cloaked with.
But when you come right down to it - even on this issue of why you feel that way - I think you just shouldn't give a shit.