With regard to your brother, I am very happy to take your word for it that he isn't racist. I'd be surprised if he was because he's close kin with you and I know from your views over many years that you're nothing but decent. I don't think he is thick either. Probably most people wouldn't call me thick either, but I've got to tell you, I am on occasion immensely thick. Ask me to do any DIY task and I am not just lacking the physical skills, even how I think about approaching the task is usually embarrassingly stupid. That's the thing, when I call Leave voters stupid, it's not that I think they are actually generally very intellectually lacking. It's not that I think that
compared to me they are intellectually inferior at all. It's specific. It's specific to them and it is specific to the context of Brexit.
I do think he is ignorant, but let me expand, lest you misunderstand and get agitated.
Merriam-Webster defines ignorant thus
1a: destitute of knowledge or education
//an ignorant society
also : lacking knowledge or comprehension of the thing specified
//parents ignorant of modern mathematics
b: resulting from or showing lack of knowledge or intelligence
//ignorant errors
2: UNAWARE, UNINFORMED
I don't think he lacks intelligence nor would I assume he lacked education, at least not in any general way.
I do think he probably lacks knowledge or comprehension of things
specified eg the EU, International Trade, International Law, supply chains and so on. Apart from a very small number of the flexcit (EFTA/EEA) advocates, that is unfortunately true of all Leave voters.
Other than general ignorance about the EU and Trade in general, why your brother is stupid, in this narrow specific matter of Brexit, is shown by the very reasoning you have given for his vote.
'he decided that he never agreed with a parliament based on 27 different cultures and economies was too difficult to manage. He saw the end of steel, Ship building, ICI, and other heavy industries down to the ease of movement, car plants transferred to Poland and other eastern European countries as avoidable'
There is a perfectly reasonable point regarding 27 different cultures, but it seems to me the majority of his objection to the EU is on
economic grounds, whether that is the difficulty of managing 27 different economies or the role he saw the EU playing in the demise of the UK steel, shipbuilding, chemical, car manufacturing and other heavy industries.
So I
think, making some reasonable assumptions about your brother, that there are some internal logic contradictions going on in his reasoning.
I'm assuming it isn't the factory owners having to move abroad that he felt sorry for, but the workers and the effect on the local community. He had never voted Conservative before the last election and he is your brother - siblings tend on the whole to share a lot of similar values and views. That suggests he is also left leaning. I, and many on the Left, the majority on the Left in fact, were also angry and saddened at the end of steel, Ship building, ICI, and other heavy industries, including some car plants transferred to Poland and other eastern European countries, no doubt made easier due to the Four Freedoms central to the rules and structure of the EU's Internal Market. Our values aren't that far apart, so it is not his
values that I think are stupid, it is his vote. How, despite sharing so many common values, the route his decision making process led him down, was in fact the stupid one to reflect those values.
I probably disagree with him on the degree to which the EU is responsible, but that is a genuinely contentious area and if he is of the opinion that the EU was at least as responsible as, say, the Conservatives under Margaret Thatcher, then fair enough.
I wonder, though. Was that his opinion at the time? Your brother must have been baffled at all the marches and protests at Westminster and Ben Elton blaming the Conservative Government rather than everyone marching on Brussels?
Or has he changed opinion since? Because if not and his motivation for his Brexit vote was largely because he could not forgive their role in the demise in UK heavy industry then, ahem, he just voted Conservative.
Even if he has been consistent with his views or changed them, his main rationale is economics. Well, it is only logical that he therefore looked at the overall likely impact of Brexit on the economy. That means not what being a part of the EU back in the 80's might have done, but what leaving it would do today. No credible evidence was offered by the Leave campaigns that Brexit would improve the economy. The Economists for Brexit claimed it would, but wouldn't show their workings because when ever they did, the scrutiny it allowed showed their modelling to be farcical. There were plenty of studies, sector by sector, including the car manufacturing industry (EU membership can be demonstrably shown to have been hugely beneficial to us by the way), which shows in purely economic terms, the odds were that leaving the Single Market was going to give us a significant negative hit.
Even if people didn't vote Leave for economic reasons and it was the impact of the EU and EU migrants on British culture that was their main motivation, ignoring the economic impact is bad reasoning, because it was definitely a consideration, because it
had to have an impact.