It all comes down to which sources they chose to use. I've seen articles citing certain"news" outlets, but when people linked a video with actual video evidence i.e. the event in question rather than an opinion it get cut down because "not a reliable source".

Recently, someone mentioned a book by Mike Cernovich, and the article on it was marked for deletion, even though the book existed...

His page was full of terms like alt-right, manosphere and so on. Not only do those terms not have a clear and objective clarification of who or how someone belongs to them they're mostly used as a smear. I can't tell you much about him, because I have to rely on wikipedia for those type of people, and his article seems to be mostly opinion article based.

It's the tragedy of the commons, we have this wonderful resource for knowledge and people began trying to get the most of it to further they're agendas destroying it in the process.