I also fully agree with this comment!
I believe thid are the works they are referring to:
Student-teacher relationship which id clearly grooming:
Part 1: http://www.mangago.zone/read-manga/yugami_hajime/
Part 2: http://www.mangago.zone/read-manga/kyoushitsu_no_yugami/
The Henai series:
http://www.mangago.zone/read-manga/henai/
http://www.mangago.zone/read-manga/henai_maotoko_hen/
http://www.mangago.zone/read-manga/henai_fumouhen/
It didn't get toxic until well into the manhwa, though. The first 40 chapters or so were a pretty good bdsm story, and then it got all twisted. All this while, it's just been advertised as a femdom story, so by the time you realize it's toxic you're kind of already invested. Even then, as someone who enjoys twisted stories, this just has awful, awful character development and the story doesn't even acknowledge that what anyone is doing is worng. I mean, Doona is literally portrayed as a strong indepndent woman when her independence is literally abusing men.
Seen a few comments complaining about those that are critiquing this story with the usual "It's fiction" retort. Yes it's fiction, and there is good fiction and bad. Like someone posted, fiction is a mirror to reality. The author is using her fictional work to promote a lot of toxic aspects of a capitalist society, that image is the most important thing, that gender roies are rigid, and the power lies with wealth not skill. The author is using "bdsm" as a way that many abusive men in real life do, it has widely been reported that "she wanted rough sex" "it was bdsm" is used as defense for men who abuse or murder their female partners. Having Doona fill this role doesn't make her a "strong female lead" and having Doona's "character growth" being her so hung up about her ex not validating her 24/7 whilst she puts nothing into the relationship and emasculates her male partner. She ends up with a younger, naive character, who will never be able to be her equal and grow together, she expects him to play the role of submissive housewife, providing her with sex and being a maid... that's not an empowering female character.
Harada has been brought up as a comparison to "dark" stories. But what Harada does is challenge a lot of controversial tropes, by showing how normalised abuse is in yaoi. Harada must be the only yaoi author to portray the "student x teacher" trope for what it is, grooming. And their "Henai" series literally parodies yaoi's obsession with glamourising rape.
As it is fiction, author's, good author's have a platform to hold a mirror up to society and challenge it. For me, this was best seen with Yamashita Tomoko's works, which challenge the sexism women face. Saezuru too, challenges the yaoi idea that sexual abuse and neglect is just something that can be forgotten easily, instead the author has spent 10 years crafting characters like Doumeki, Aoi, Yashiro and how all three of them being survivors has impacted them.
The author isn't holding a light up to the "ills" of society, she is depicting them and reinforcing them. Readers are criticising the author for not just sticking to a one shot "mind break" hentai manga, as it would have achieved the author's goal of ruining Minho. Instead they created a 100 odd year old manhwa, that readers have been following for years, in the hope that the characters actually develop and the author actually challenges the social structures that the character's live with.