You're making a huge leap by assuming this is because such a subject isn't politically correct or whatever. There's many more likely explanations:

• You have phrased the search in a way that people expressing that view wouldn't be likely to use, yet is similar to how people holding contrary views would express theirs. I think that's the case here. If you search for “gender does not exist” or so, you may get the results you want.

• Google's results are customised based on what they think you would be interested in.

• Content from one side of a contentious topic may be less popular online and/or not linked to as many authoritative sites, and thus have a lower PageRank.