They are the result of thousands of years of evolution. Their bodies are perfectly suited to the environment their ancestors have lived in for millennia. Yet they think they can move to a completely different country and expect it to be healthy for themselves and their children?
Let's look at skin pigmentation.
Darkly pigmented:
Suited for places where UV radiation is high such as high altitudes and places near the equator. Dark skin was necessary for places of high UV radiation because it prevented the destruction of folate by UV radiation and thus prevent folate deficiency, whilst the skin is still able to produce the right amount of Vitamin D since the UV radiation is so high. Folate deficiency can affect the fertility of both males and females and can lead to potentially fatal birth defects. People with light skin moving to these places will have reduced fertility and birth defects of offspring because the folate nutrient in their blood vessels would be destroyed by the UV radiation as their skin cannot block much out.
Depigmented:
Suited for places where UV radiation is low such as low altitudes and high latitudes. Lighter skin is better for places of low UV radiation because at these low levels there is not much sunlight for the skin to produce Vitamin D, necessary for calcium absorption and healthy bone growth. Lighter skin would allow more UV radiation and thus aid Vitamin D production, whereas darker skin would prevent the production of sufficient levels of Vitamin D. Lighter skin in these areas has evolved to ensure maximum Vitamin D production in conditions of reduced sunlight. Vitamin D deficiency has been implicated in diabetes, auto immune diseases, and viral and bacterial infection. People with darker skin moving to these places would develop Osteomalacia and produce offspring who may suffer from Rickets.
As far as skin pigmentation and migration goes, it is bad for a person's health to do so and the health effects are very taxing on the healthcare in the country people are emigrating to, so in Britain's case large amounts of our money are being wasted on immigrants not suited to our environment.
Therefore it is sensible to stop all immigration outside the EU, or separate people by skin colour and place them in their suited environments.
Discuss.