Malyis,
We cannot fail to be influenced by our view of history and personal experience. As a middle aged person of Jewish descent I do laugh when people argue that my security will be better if we are a member of a block dominated by Germany. It is not that I think that modern Germany or most Germans are anti Semitic, as I don’t think they are (although still suspect Austria and a few Eastern European nations of being pretty anti Semitic). It is just that the UK has a tolerant tradition going back an awful lot further (some of my family immigrated into East Anglia in the 17th century).
The extent to which bigger is better is very much open for debate. A large integrated banking system looked fantastic until 2008 when the interconnectedness meant that they all failed together.
Equally, from a historical perspective, trading blocks (and especially those with a common currency) have all failed bad the US where there is a common government, language and taxation system.
It can be argued that, in the modern world, a national economy is not big enough to compete. However, equally, no one is arguing for a world trading block, those in favour of the EU seem to think it is the magic size. Well, maybe, but maybe not. China and the US seem to pretty much work as one economy without much in common at all (look how much money China ‘lends’ the US so that they can buy China’s goods, they are totally interdependent).
As for immigration, when people’s views are analysed, it comes down much more to the ‘citizens of somewhere’ argument. This is not just true in the UK but a lot of the EU where a portion of the domestic population resent immigration, hence the rise of the right wing nationalist parties. When challenged, what these people mostly resent is not skin colour or place of birth, but cultural dilution. Generally British (or Dutch etc) immigrants are not resented where they buy into local culture and values.