In kpop communities I've been a target of hate longer than many 2nd gen idols. Basically, when it comes to anything, people always want to go into extremes because they innately frame things as "good" vs "evil". With their side always being "good", no matter what they do.
Since reality is actually a lot more complex, people will apply these simplistic worldviews to something as simple as a comment or just have a different opinion.