Depends how much there is of a "police are useless" attitude (as well as with the landlord). And even a (relatively) anti-gun person is going to be somewhat likely to be happier to have one than not in various circumstances, in the US.
(Over here, in the UK, your average person wouldn't talk so easily about gun details and UDs/ADs, even our cops are overwhelmingly unarmed, where my experiences of the contintent (Germany, your Netherlands and France, as the main swathe) is that while the populace don t go toting (or, one presumes, concealed-carrying to any great degree), the police all seem to have sidearms. Whereas this is an extreme rarity in my local experience.)
I mean, I'm wondering what a gun will actually do, in this circumstance, except add more complications. The sex-pest might just be picking on the one person who hasn't yet waved a gun(-shaped object) in their direction after the first rude interuption. But, culturally, it's all frankly foreign to me. If I thought any of my neighbours had a handgun[1], I'd probably feel no less surprised than with you and your rocket launcher incident, yet without any expectation that there'd be plenty of unfettered voyeurism going on in the absence of such 'safeguards'. (Maybe I just don't live near such a hotspot of
lasciviousness and ne'er-do-welling, of course, and there are always going to be clusters of any given bad behaviour if you look for it. Whether even the same building codes and practice exist to even make this an exploitable issue, elsewhere.)
But everyone has to deal with the situation as it seems fit for them to do so, within a given degree. Sounds like this degree of dealing with it is pretty much normal, by FD's current circumstances. Which might be a different problem, less easily solved.
[1] Less surprising if nearby farmers have shotgusn, but I wouldn't even assume that to be a given. Probably as likely to get "a man in", should there be any significant pest-control issue (which needs any such solution) in many cases. Like they'd hope to get a police response if they had human intruders.