Ask yourself

Ask yourself, how much respect would you offer the idea that Earth is flat? Not much, though you may not outright mock the person promoting that idea. Most likely, you’d just ignore the guy and move on. But what if it wasn’t just one person? What if you had a huge swath of the country which thought there was legitimacy to this idea? Those people vote. Those people have a voice. They can tell their senator, no, we don’t want funding for NASA because it predicates its gravity boosts for its spacecraft on the idea that Earth and all the other planets are not flat. Do you think you might have a problem with flat-Earthers then? Do you think maybe you’d stop giving them the impression that what they thought was legitimate?

This is why scientists (and atheists) are so willing to laugh, mock, and dismiss creationists.