Right, so you don't like the 'Flat Earth' theory...ok. I wonder why it's a problem if other people believe in it though.
Are you really suggesting that folk who believe in such things should be locked up in mental hospitals? C'mon!
And 'cognitively able' but not believing that they are sick? Kinda like they 'look normal' but are actually sick and don't know it....but you do?
I don't get your logic, but we can leave it at that, unless you wish to add anything or carry on.
The difference between facts and opnion is simple. The first doesn't require any logic, the second one does :)