He is English primarily so he is used to talking about England, in just the same way that the Welsh, the Scottish or the Irish are used to talking about themselves if they're from Wales or Scotland or Ireland. It's natural for some and shouldn't be considered as just another excuse to criticise them.
It seems ok though to criticise leavers as being too thick to understand what they're voting for but I wouldn't be surprised if a fair number of those who voted remain had just as poor an understanding of what they were voting for. ( We are not seeing vids of those on here though are we). Someone I know voted remain because she was very frightened if we left the EU WW3 would start because Cameron had implied as much. Nevertheless, unless you want to be discriminatory, everyone in the country has a vote and all votes are equal, whatever their level of intelligence and understanding.
You are right on this. Many people who voted Remain will have done so for poor reasons, and as I alluded to, we do not really know who was 'right' anyway. The Remain campaign was really poorly fought in comparison with Leave, also. However, I have paid close attention to the different voting parties and underneath the campaigns, virtually everyone who looked at the question in detail, with a proper attempt to work out what was best, and without a personal agenda, voted Remain - and many of these expressed why in a very convincing way. The same is simply not true for the Leave voters. I have not seen a properly stated (never mind convincing) economic argument for voting Leave. I have not seen a convincing argument that leaving helps us address any problems that we face... certainly not soon, anyway. Am I to believe Leave all have better strategic thinking for the long term? Based on what?