Towards the beginning of the expansion, I had viewed Venat through rose-colored glasses because of how she was presented. These days my view is a darker shade of grey as elements present through the story would give you the ability to interpret her in a more negative/evil light. And as you have put it, the presentation itself is capable of changing someone's opinion of her to a more positive tone. The necessity of suffering she introduced along with the immediate aftermath of the sundering is extremely jarring compared to her overall messaging and causes Venat to have a large amount of cognitive dissonance. As such, it is why I am not as critical of people who view her negatively.
If true, this would make the individuals you are referring to extremely detestable. I have said this before but individuals who behave in this way disrupt how the forums function and will cause newer players to be dissuaded from interacting with them directly. While I am not opposed to debate as people are entitled to what they think, I am opposed to people like the ones you are describing here.
Vitriolic behavior as you are describing is something I would expect out of some of the worst cesspits of the internet. It is extremely vile and the individuals who are participating in said behavior should be ashamed of themselves. With that said, I suspect they are not ashamed of their behavior either...but that is something I would not know.
My apologies you had to deal with such detestable people.
Generally, I tend to lay the blame on the writers here, and as Venat is likely the most affected from this, she is a character I expect to see a wide variety of opinions about her character. It is something that has pained me greatly because it caused parts of the game that use her as a central figure to feel...incomplete or lacking to me. I have no direct issues with people who like Venat or dislike Venat, I just need some semblance of an argument where I am able to reach whatever the other person's opinion is without needing a large number of logical leaps.