It is, of course, true that predictions aren't perfect. The problem with the Brexiteers is that they assume that not only are they wrong, but they are wrong in one direction only.
Ok my Mum voted for Brexit can you cite her please?
The term I used was Brexiteer, not just someone who voted to leave. Sure I didn't define Brexiteer, but it is no more congruent with all leave voter than the term Remoaner is congruent with all remain voters.
So in my view a Brexiteer is someone who vocally supports leaving the EU, basically as an act of faith, and refuses to acknowledge the possibility of any downsides, raised particularly by experts. Likely to be the same people who routinely use the terms 'Remoaner' and 'Project Fear'. Brexiteers are characterised by a kind of evangelical approach based on faith rather than reason or facts. So if you Mum refuses to acknowledge the possibility of any downside, then she is indeed included in my statement. Perhaps, on the other hand, she is much more realistic - perhaps accepting and worried about destabilising and negative effects that are already happening, just as predicted, and the likely ongoing negative effects of brexit as it actually happens. In which case she wouldn't be included.
But the kind of evangelical, act of faith statements one might expect from a Brexiteer might include continually parroting out nonsense about the 'economy still being bigger after brexit', while refusing to acknowledge that the comparison is just that, a comparison between the economic state under brexit compared to what would have happened if we remained. No idea who might come out with pointless comments of that nature regularly.