to the clearly unemployed alumnus who graduated nearly 20 years ago and still spends as many as eight hours nearly every single day on one of the student computers in the library watching YouTube music videos and doing who knows what else:
We are not friends. Just because I have to log you in as a guest on the computer every time I work and once engaged in an exasperated debate with you about why not every single site on the web should be accessible only by paid subscription, does not mean I am interested in getting to know you better or sharing any of the details of my own life with you. I'm not even interested in small talk. Pretentious as it may sound, I really don't see what I might have in common with someone at least 25 years my senior who has no hobbies other than the internet and doesn't seek to make friends with people his own age--particularly when most of the opinions he expresses are in opposition to mine or at the very least clearly misinformed.
I don't feel threatened by you so much as a little creeped out. Pleasantries are one thing; I have no problem with politeness, but approaching me as you did today (while I wasn't even on the clock) and ask if it's "okay to talk" to me is a little weird. Continuing the conversation by saying that you have four sisters and have "dated a lot of women" and that, as a result, you're good at intuiting a woman's attitude/energy/whatever, does not help your case. In fact, it serves as further evidence that you've overestimated the intimacy of our acquaintence.
At least you were able to (accurately) determine that, in previous encounters, I did not, in fact, wish to talk to you. Though I tend to believe that even the densest of people -- men or women -- would get the hint about unwelcome conversation when the targeted conversant is purposely giving one word answers and/or looking for an excuse to exit the conversation/geographic location.
Furthermore, I can only hope that your expressed belief in every woman having a website to answer whatever "frequently-asked questions" she receives (since you understand that "women get a lot of questions") is merely the result of a bizarre and poorly-thought-out attempt at conversation, and not the creepy and intrusive display of sexism that it actually was (even if, as you suggest, the answer to those FAQs is "none of your business"). I didn't have the desire or the time to further discuss the idea with you, so perhaps I'll never know.
Your intelligence is clearly at least adequate enough to allow you to graduate from college; why not take more classes and come to campus as a student? Why not take up a research project (you know, where you take notes or at least carry a notebook, since you don't have access to our printers as a non-student) or some hobby that gets you up and moving around (particularly away from campus)? Why not use your extroversion to get involved with, say, a volunteer organization or some kind of PR instead of wasting it trying to befriend clearly-uninterested library student employees or luring in the less innocuous companions you occasionally bring to the library with you? At the very least, you could go upstairs and look at the actual books or newspapers on occasion.
It's true that I don't know a lot about you, but things that I do know make me pretty certain that I'd like to keep it that way. I'm never going to hang out with you, or even go for coffee, and I'd like to make sure you "intuit" that it will never even be an option. Thus, I see no reason to further develop our acquaintance. I think a simple "Hi, how's it going?" is the most indepth conversation we really need to have.