This whole thing is absolutely awful, but to bring some understanding to the table as to WHY they are doing this, it's because of the way women have been portrayed in yaoi throughout its history thus far. They are either 1. homophobic evil creatures that aim to break up the couple somehow because they think it's bad or disgusting, or 2. romantic rivals that aim to STEAL OUR MAN!!!!!
It is a straight up sexist way of depicting women, and it ends up affecting the way young girls grow to feel about other girls as well as themselves. They're not depicted as individuals with complex feelings or opinions of their own. They are used to symbolize concepts (homophobia) or they are objects. Shallow punching bags for the fans to take their anger out on.
The best way to combat this view of women is to create something that defies this depiction in the media. Just create strong women, weak women, complex women, women who have a reason for what they do. Women of all kinds! Depict them as people. It's okay if you have a woman that gets in the way of the male romance, too, as long as you develop her personality and make her a person, not an object.
For example, I actually intentionally "female shitlord"-baited my audience once. I introduced Nunia from Bloodroot as if she was gonna be a threat to the gay romance. Then it turns out that she's a lesbian who's in a happy relationship and has better shit to do with her life than to get between two gay men. Oops.
This was something I did, knowing how human psychology can work out. If I introduce something in a manner that goes along with audience expectation of what women in yaoi are like, and then shock their system with new information, it forces the brain to think in new ways and reconsider their patterns. If I hadn't lured the minds that I intended to affect into what they considered homely and safe territory initially, I may not have opened them up enough to be able to reach out to them.
Sure, we can all preach gender equality and the like to the people that already agree with us, but what is the point in that? The people we truly need to reach out to are the ones that still carry the problematic tendencies.