I think you're being unfair to Dennett. He actually has availed himself of the findings of other fields, and has been at the consciousness shtick for decades. He may not agree, but it's unlikely he is unaware.

And when did he say consciousness was nonexistent?

Cite? That seems a rather odd thing for him to say, and not particularly in his ideological interests.

Dennett writes about how detailed visual hallucinations are impossible.

Cite here? Again, except for supernatural bogeymen, my experience of him is that he recognizes that all sorts of mental events exists, but maybe not in the way that people suppose.

They simply pretend that the things that don't fit in their worldview don't exist.

Not accurate. If those things don't fit in their world views, they don't exist in them, so they're not pretending.

On a general brouhaha with CHapman, I seemed to miss most of that. He did one post on Jaynes and A_p, which I read as I've always been interested in that particular branch of Jaynes' work. But the post made a fundamental mistake, IMO, and the opinion of others, and I think Chapman admitted as much before all of his exchanges were over. So even with Chapman running the scoreboard, he's behind in points.