At this point, anyone who's still a Brexiteer has engaged in some extremely selective listening. There's no point in having a discussion with someone who won't seriously address the entirely likely problems of Brexit, both as a concept and how it is currently being done.
(I mean, Brexiting to the status of Norway might at least have been feasible, but that's now a long way in the rear view mirror.)
I'm personally very worried about sentiments like the one you express. The smug complete dismissal of another's viewpoints, complete refusal to even just listen, generalizing over all people with the same ideas...
Opinions like being in favor of Brexit are not in any sense as fundamentally objectionable and unacceptable even for disucussion as, for example, nazism or racism. Political divisiveness is a significant issue, and behavior like this is only going to make it worse.
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.
This is the same kind of shit as the faux neutrality news reporters are held to on scientific topics. But, suddenly, because it's political we should then listen to their shit viewpoints?
If you don't want to listen, I can't force you, but what's the point of poisoning the discussion so the people who do want to listen, like me, don't get a chance to? How can you even say their viewpoints are "shit" if you don't know what they are, what the nuance is, the context. Is that opinion informed, or is it from out-of-context snappy soundbites repeated from your filter bubble?
This dismissal of an entire group of people who just happen to have a different point of view to you is a major part of what is so toxic about the Brexit debate and political discourse in general.
There is always a point in having a discussion with someone, even when they are severely misinformed and blind to their own biases because neither of those makes their perspective void, just harder to understand. But gaining that understanding is the only road available to you that can lead to them changing their perspective. Additionally, no matter how much sense you make to yourself and how much nonsense the other individual appears to be spouting, the moment you dismiss even the possibility that you yourself are wrong and that they could have a valid point, albeit poorly articulated, is the moment you throw away the claimed high ground of being rational.
(I mean, Brexiting to the status of Norway might at least have been feasible, but that's now a long way in the rear view mirror.)