I, personally, think that loads of arguments have been made for and against immigration. For me, the official reports showing that immigration has been good for UK, is sufficient.
It wasn't the initial reason that I became involved. I only became involved because I was inflamed by the racially motivated arguments that were being used, and still are, (joe, stand up and take a bow for your Roma comments). We all have cognitive biases based on our own experiences. Joe, perhaps has had a couple of experiences with Roma, and now fervently believes that all Roma are out to get him. (Tell your doctor about your fears)
When the EU proposed free movement of goods and people, it didn't mean that one has to prove one's wealth or one's skills, or one's lack of criminal record to be able to move between countries, although no doubt, some criminal record is disclosable, I'm not sure.
It means that I'm free to settle in another EU county, if I choose. As long as I do not exploit the benefits system, illegally or otherwise, then that's OK.
If some potential criminals choose to try and exploit the UK's benefits system, then the law should be applied. If the law is not applied adequately, then it gives rise to the kind of prejudice demonstrated recently on this forum, i.e. an unofficial discrimination.
Unlike some other countries, where an official discrimination was/is present, e.g. Germany and the employment of "gastarbeiter" "guestworker" who has no citizen type rights. (As typified by that programme on UK migrant workers in Germany some years ago)
Of course other prejudice was/is based on fallacious undestanding of the different cultures, black, muslim, oriental, etc.
There are a minority of all sorts, of all races, cultures, etc that do not respect the law, and these should be dealt with. But you can't reasonably tar all the members of that race, creed, culture, religion, etc, with the same brush. To do so is to fall prey to your own cognitive biases, or worse still, to fall prey to other's cognitive biases.
An attempt to ferment your cognitive biases in others is to insult their intelligence. An attempt to ferment racially motivated violence is an insult to society.
