I fully accept that people may have genuine concerns about immigration. Some of those concerns may be 100% valid. Some may be based on misinformation or poor understanding. Regardless, I can accept the fact that some people have concerns.
But if people do have concerns, there are ways of expressing and addressing these properly. Peaceful demonstrations. Lobbying MPs. Or even standing for election.
But as soon as people make the leap from expressing legitimate concern about government policies to intimidating and attacking innocent individuals who have no influence or control over those policies, that is when "concerns" are no longer relevant and common or garden racism takes over. If people weren't fundamentally racist, why on earth would it even occur to them to do this?
If I am unhappy about decisions affecting my community taken by my local council, my first thought isn't to go and beat up my neighbour in order to make a point. Most people would recognise that such anger was utterly misplaced. Why is it that people don't seem to recognise that the anger towards migrants/asylum seekers/ethnic minorities/muslims etc is equally misplaced. Why are so many people saying that they understand the reasons for the violence ever though they don't condone it.
I don't think it's at all understandable that someone with grievances about government policy would think that throwing bricks at a mosque or setting fire to a building full of people will help to resolve the issues that they are concerned about. The people that they are targeting are not in a position to change anything. There is no logic to this thinking, so why do people's minds go there? As far as I can see, the only possible explanation is racism, pure and simple. The "genuine concerns" are nothing but a cover for thuggery.