Being in favor of Brexit a few years ago was defensible - I used to be a moderate Euroskeptic myself. Being in favor of this Brexit here now is exactly what you're talking about: it requires dismissing all the other viewpoints and possible problems, such as the Irish border and what happens to people from whom freedom of movement is removed.

"Smug complete dismissal of another's viewpoints" is exactly what the Tory government has done, and exactly why it's got into such a mess.