Quick (and no cheating), name the sample from Fugees - Ready or Not
I didn't read this whole thread, but the sample is Enya's "Boadicea", one of my favorite songs by her. That whole Fugees album is still good.
Personal red flags would be people who mainline K or J pop, they are usually zoomies who haven't had enough time to diversify what they like in music, or weird dead eggers who get moist to twinks. Either way trying to talk about music to them is either a chore or a waste of time. There are occasional K/J pop songs I like for mindless background music, but none of the major bands have much depth, but that's part of the fun of them if you don't take them seriously.
Also black metal purists. I say this because years ago I used to be one. There's a lot of black metal out there that's just like top 40 dreck for the genre, but there's a surprising amount of actual good music in the genre, if you like heavy shit.
Speaking of that, top 40 anything. Anyone who thinks this stuff is deep or makes an intellectual connection with them hasn't listened to much music, or is just shallow, usually. I like some pop bangers and whatnot, but it's not like Swift, Ava Max, Dua Lipa or Lady Gaga is gonna make me sit and think about their music beyond whether it's just a fun pop song.
Indie stuff is very hit or miss, and usually tends to make fans think they are smarter than they actually are. The types of people who make that type of music their identity have long been laughingstocks due to their unwarranted arrogance. Still a lot of good music in there if you dig, even if these types are the biggest red flag wavers in my opinion.
Rap/hip hop people can either be chill as hell or as bad as metal purists. I can't really say much, because I've never really gotten into the music itself, it never has done much for me.
Country also has never done much for me, especially the modern stuff crossed usually with buttrock or pop. I like really old country music, but I might listen to it like twice a year at most.
Folk music is strange. The people really into it can throw up all kinds of red flags, unless they are into the old resurgence of the 60's and 70's, a good example of the kind of stuff I like from back then would be bands like Fairport Convention. Newer folk music is full of all kinds of off base political garbage.
Really, a lot of the red flag stuff has been brought up already in this thread, like hardcore Tool fans, Juggalos, Feminazi punk, crust punk, all those people who would be walking flagpoles for "zomg run away". But music is so subjective that usually, if someone is too into something, even if the music they like happens to suck to you, it's a part of their personality that they like it for whatever reason. When they make it part of their identity like swifties is where you see problems.