Here's a post of mine on a different thread from last week that explains my reasons (regarding immigration) for wanting to leave. I'll include the comment that this was in response to, I'll leave the poster anonymous though.
"the Beakers arrived circa 2,500BC, the Celts arrived some time after that, the Romans arrived in 55BC, the Saxons arrived sometime after 400AD, the Vikings started coming in the 7th century, the Normans arrived in 11th century. These guys often came with armies and the intention of dominating the locals, and yet the British far right, most of whom could probably do with a history lesson, integrate this into part of their national identity. In contrast, the migrants arriving today are like "can i have some work please, i'll work for cheap", or alternatively "air strikes left my house in rubble, can i please live here?" and people are freaking the **** out as if the viking hordes are on the shore."
"People really don't care for this narrative. The liberal 'everyone is an immigrant' nonsense really doesn't have much impact. As you say, the last wave of 'migrants' came in the 11th century,one thousand years ago. Are you seriously suggesting that nearly 1,000 years of relative isolation (compared to today's standards) hasn't had an impact on overall British ethnicity? Why do British people look different Scandinavians, French people, the Dutch and Germans if we are all among us a random group of mongrels? There is even a marked difference between the British Home Nations and to deny this fact really is regressive and degenerate social engineering.
Regardless of that, British 'isolation' certainly has had an impact on our culture and national identity. Many of the migrants today simply don't hold European values, let alone British ones, and the arrival of these people into our societies is damaging to our social values and structure, the products of 1000 years of shared history, culture and stability.
By all means let's bring in the world's civilised people - The many people from the Commonwealth who've had a taste of British customs and concepts such as free speech, parliamentary democracy, common law, institutionalised fairness and the like. Indians, Nigerians, people from the Caribbean and of course the Australians, New Zealanders and Canadians. People who share our values.
There are a multitude of reason why people oppose the levels mass immigration we have seen in the 21st century. There are legitimate economic fears, concerns about national infrastructure and the like. The way in which many people, like yourself, immediately throw accusations of intolerance and even racism really is inappropriate and often times part a concerted effort to limit discussion. We can discuss the aspect of purported cultural intolerance in Europe to migrants however as it seems that you are alluding to it in your post.
Europe, whether for better or worse, is undoubtedly the continent home to the largest number of liberal and secular people and countries. Historical events such as the Enlightenment and the decline of religious fundamentalism paved the way for the flourishing of arts and sciences, the adoption of 'liberal' policies, the implementation of wide-reaching educational programs, the conception of modern charities - all the sorts of benign social systems that are lacking in the underdeveloped regions of the world.
Over the last few decades we have made great advancements in Womens' rights, LGBT rights, animal rights and environmental protection. These aren't trends that can continue however as we continue to import people who have beliefs fundamentally incompatible with the products of hundreds of years of advanced European civilisation.
Britain has been the most successful country in the world regarding modern multiculturalism. The Afro-Caribbean community, Sikh community, Hindu community, East Asian community and many others have mixed into British society comparatively well. This is because there isn't the fundamentalist, poisonous, fascistic and oppressive ideology of Islam preventing them from abandoning backwards customs in favour of civilised British and European societal norms.
We should never tolerate the barbarians of the Middle East and North Africa who continue to practice Female Genital Mutilation, domestic violence and slavery, beheading and stoning to death and the like. The news reports of mass beheadings, live burnings, rape of women and execution of minorities and homosexuals from Syria and the Middle East are bloodier than any tale of Viking raids on 9th century Britain.
It's a shame that the one organisation that could prevent the destruction of Europe in this manner is pressing for more migration from the backwards and degenerate regions of the Earth. That is why I shall be voting to leave the EU. It might be too late to save Europe but we can still save ourselves."