I completely disagree. If the In campaign are allowed to postulate about all of the possible negatives of leaving, surely the Out campaign are allowed to postulate as to the potential negatives of staying? I've said all along that this is a once in a generation vote and thus we need to vote not on our current relationship with the EU, but on the trajectory our current relationship with the EU is on. I don't have the stats to hand, but have read that we are the nation that disagrees with the EU decision most often - do we really have that much in common with other EU states?
On that trajectory, I don't think it's at all unreasonable to suggest that Turkey will be joining the EU in the near future which will open up a land border between the EU and the likes of Syria and Iraq. Our economy is also outperforming most in the EU, so we can expect to pay more into the coffers in the future given that the amount each member pays in is dependent on how well its economy is doing. TTIP will also come into play. Within 5 years the huge number of migrants from the Middle East and North Africa and even into Pakistan will be granted citizenship in the EU states that they have 'sought refuge' in, allowing them freedom of movement across any EU state and rendering Cameron's agreement to hand pick a few from refugee camps as useless. With that will come yet more strain on our already extremely stretched resources in housing, schools, hospitals and land.
England has a population density of 419 people per square kilometre. In Germany that is 228, Poland 130, France 105 and Spain 94. To be as crowded as we are, Germany would need another 69m people, Poland 86m, France 197m and Spain 161m! Do people really not care that we live on top of one another (check out any new build housing estate) or that our greenbelt (which IMO is pretty unique and defines our country) is being eaten away to provide accommodation for people we do not necessarily need to be in this country?
A more speculative person may suggest that the EU would like to stretch its tendrils further east into the likes of Syria under the pretence of saving it from war and yet absorbing it under Western control that frankly doesn't suit the country. He might suggest that the EU would take an In vote as a sign that the UK are ready for ever closer union and will push again for us to take the Euro just as those bastions of predictive genius the IMF urged us to do. They may even take that further and create the superstate they are striving for with member countries losing all sovereignty. These aren't things that I think will happen immediately, but they definitely have to be considered as possibilities to happen before we'd be allowed another vote on EU membership.