This is always a hot take for some reason... but... at least here in the US, society is such that men are expected to approach and ask women out first. Women sometimes approach, but it is rare and not at all expected. Nobody owes anyone a date or love or anything... But... I firmly believe that in a society that expects men to ask first... that if a man approaches and asks, he should get an answer.
The answer can be no... no thanks... hell no... fuck no get the hell away from me... basically whatever you feel and whatever you feel comfortable saying... but if you have any expectation for someone to approach you, you have to be willing to say no when someone you don't want to approach you approaches. This doesn't seem really difficult to me.
Are there men who don't take rejection well? Absolutely. There are women who don't take rejection well either. Humans are flawed, some of us more than others. And I truly get the notion that women, on average being physically smaller than men, sometimes have fears that IF they reject a man he might react very poorly and there could even be danger involved. This is true. It sucks, but I understand it.
It's just... I don't see it applied everywhere. I mean, I'm a pessimist... I expect people have an agenda if they are friendly to me out of the blue... but if I treated everyone like that all the time, then I'd have no chance of ever meeting decent people. You can't work a job that requires you to relate civilly to people if you think they are out to get you. We can't all be shut-ins... even if I want like HELL to be a shut-in most of the time... I still have to venture out sometimes and be civil and watch my back but be civil.
Bottom line. if a guy asks a woman out... she should be able to say no, in whatever form makes sense to her... and that should be it. But that means, if he leaves you completely alone after that... no complaining about "he only wanted..." or "why didn't he try harder..." or whatever. You say no, he leaves, that's how it works. And, by the same token... IF he doesn't take your rejection, your clear no... if he keeps at you... makes you uncomfortable... you get to tell other people, call for help, report him for harassment.
Consistency would curb a lot of this. I'm not saying it is right... but too many men are taught (sometimes by example, other times by gurus) that an unclear response from a girl means maybe... and that you just didn't do it right so you should try again. There are posts all over social media too from women who want to know why men don't pursue them like they used to... or why a guy asked her out, she said no, and he left and didn't talk to her anymore. While there are a lot of women who want men to leave them alone, there are a lot of women apparently who want men to try harder... and this is confusing.
There are men who are actually nice, while there are men who are good at pretending to trick women into things... this is ALSO confusing. And I get women often have more dangerous considerations than men in these scenarios. But if we aren't going to all lock ourselves into our houses and give up on the notion of friends and relationships... then society as a whole needs to figure this stuff out and learn to be consistent about expressing ourselves so we know who likes us and who doesn't and we express our interests (or lack thereof) clearly... and then transgressors can be clearly pointed out and punished for it.
For the record... for the OP... if this is a guy who asked you out before, years ago even... and you were already clear with him... and he kept going OR he tried again and you still aren't interested... then you've done your best to be civil and he is abusing that civility from you, and you owe it to yourself to seek help from others to stop him from continuing.