Aveline
These other nationalities and faiths somehow keep a lower profile?
I'm not a psychologist, but I've been giving this a lot of thought lately, and these are what passes for my 'explanations'.
Islam asks its adherents to declare their faith in their clothing, and the more religious Muslims adhere to laws about food and prayer, so they stand out more in Western society than those whose religion or lack of one don't make them stand out. There are those who dislike difference of any kind. Maybe because they are unhappy with themselves and prefer people to be like them so they feel 'normal? Who knows? They can't pick on people who look like them, or who have the same accent, as their differences aren't immediately apparent, and on the whole the bullies aren't usually very bright, so they concentrate on hating those who are more obviously different. Like the kids who pick on the boy with glasses or ginger hair, or the fat girl with spots. Then they blame the victims for 'making them do it'. They have the gall to be/look/behave/dress differently from me, and I am NORMAL, honestly, I am, so 'they' can't be normal, and therefore it's ok to pick on 'them', and if you want to be thought normal you have to be on my side.
That's one reason, I think. Another is that Muslims are sometimes in communities of relatively recent immigrants, which are concentrated in poorer areas of the country. Even in rich cities, the new arrivals tend to live in the grottier areas. Those areas still house people 'left behind' when neighbours moved out to better-off suburbs and they can feel overwhelmed when the local shops no longer cater to them, or the customs of their own culture no longer prevail. Jellied eels and t shirts give way to kebabs and saris. Despite the fact that Muslims make up something like 6% of the population, in some areas they are in the majority, and that is the lived experience of the 'indigenous' people living amongst them.
Finally, there are people who just like having someone to look down on. Whether it's 'her next door' whose nets aren't white enough, or 'poor so and so' whose husband drinks, or the ones who 'aren't what they should be' for 'having to get married', those with tattoos or big TVs - there will always be some reason why some see other people as lesser. It's in their nature. Maybe it's just that nobody wants to be at the bottom of the pile - there is a hierarchy amongst prisoners, druggies and alcoholics - and maybe some people are just judgemental. I don't know, but I think that explains some of it too.
I'm sure there are other reasons-that-aren't-reasons-but-excuses (eg in This Is England, Combo hates Milky because he's from a Jamaican family whose culture is supportive and close, and he (Combo) is from a criminally dysfunctional English family). Individuals will have their individual prejudices, but mostly I think they are rooted in jealousy, fear of being 'at the bottom', a desperate need to be 'normal' and in the dominant group, and a more generally bullying personality. In most cases these prejudices are probably buried and kept below the surface, so when the likes of Tommy Robinson comes along with a slogan or confirmation of the prejudice it isn't challenged.
As I say, that is just my thoughts, and has no basis in anything other than my musings. I'm sure wiser people will be able to shoot it down, and that's fine. I have no idea about solutions, and they are the important thing, really.