if immigration brings benefits and people want controls anyway, the benefits don't matter.
So what are you trying to say? What I read above is that if people want controls on immigration, we should act on it... regardless of any
misinformation. People are going to want the best solution, and if they are fighting for something that they feel is better, when it is clearly not, it is because they are misinformed. UKIP have had an incredibly strong campaign of misinforming people, by focussing a lot of unwarranted negative attention on immigration, whilst failing to recognise any of the real problems troubling society.
I never said parties can scaremonger and it's fine (over any issue).
You are correct, you didn't explicitly state that. That said, you clearly see it acceptable for policies to be put through, even if it isn't beneficial, just because a very noisy group of people want it, regardless of any facts or evidence opposing it.
I never said demand for immigration controls "may be due to misinformation" either.
Again, refer to the section quoted at the top of this post. People want the most beneficial thing (I think this is a fair assumption to make for the vast majority of cases - there is always going to be a minority group of people who will let their prejudices get the better of them and act in a way to be xenophobic, but I am not referring to them). If people want controls, they believe that it will be beneficial. If it won't be beneficial, then we need to remove any misguidance. I know this is a democracy, but allowing the right (be it media, or political parties, although this is not a criticism of the whole right wing, just a small influential part of it) to introduce xenophobia, and to then act on it because it is now in the public opinion, is not acceptable.
Immigration has been shown to benefit us. It stops the dependency ratio (the ratio of dependants such as the young, elderly, and unemployed; to the number of people they depend on, those in employment) falling out of whack. They have contribute more to the economy than they have taken. The probability of the population of Romania all moving to the UK, which would definitely be a problem, is akin to the probability of a mutation causing a series of superhumans that will destroy humanity. It isn't going to happen.
If immigration does begin to occur on a level that is damaging, then of course something should be done, and we should definitely introduce controls. There is no evidence to suggest that this happening, or that it is going to happen in the near future (Daily Mail articles, or some shitty neo-nazi blog you found doesn't count, Cal), and to act on the whim of a loud hysterical minority would not only be foolish, but damaging.
I understand the concerns about immigration. Immigration, and the acceptance of other cultures, is something that is part of being a developed society, however, and as much as many will fight it, it is important to distinguish between what is fact, and what is the "reckon" of closet xenophobe who will use minority groups as a way to unite and mobilize large groups of voters. Many of us are not of the opinion that we should let everyone and anyone in - and we don't quite, as we don't have the visa-less system, with no border controls, that most mainland EU countries to have (in general, anyway).