I think they know it's round but they just want a spotlight onto their dim lives.
Intelligent people question the depth of their knowledge but ignorant people believe they know everything, or words to that effect.
We can only do our best to educate our children (and theirs) to think critically, and hope these ignorant people remain a minority. Sadly, it often seems that there is no guarantee that they won't win. But I will also add that the young people, as exemplified by the Parkland High School, give me much hope.