This is what happens when we cede terrain to these idealistic and demented pressure groups, such as the feminists and the racialists.
I firmly dislike works-in-theory fails-in-world idealism. It's a terrible thing, it causes all sorts of hell and misery.
That said, you're probably getting downvoted because you didn't back up your claims to add to the conversation much, and generalized too much. There's sane feminists, and crazy radical feminists. Then, while "idealistic" conveys information, "demented" doesn't add anything. You'd be much better served just pointing out what the dementia specifically is, and dropping the word demented entirely as it's just mudslinging. So, I reckon if your comment had read more like:
"This is the end result of ceding terrain to people who are highly idealistic but don't care if their plans work in the real world and don't think about the secondary effects of their actions. For instance, take Radical Group XYZ (link to Wikipedia) - it sounds like a nice cause at first, but it's done a lot of damage." I think that comment would get upvoted quite a lot, as I agree with your general sentiment but slightly disagree with its presentation (I upvoted you though, you were -2 when I came along).