Cameron did not say that. He said "Can we be so sure peace and stability on our continent are assured beyond any shadow of doubt? Is that a risk worth taking?"

Cameron did not say that. He said "Can we be so sure peace and stability on our continent are assured beyond any shadow of doubt? Is that a risk worth taking?" which is absolutely valid. It is forty years since there was a fascist government in Spain, 30 years since half of Europe was run by authoritarian communist regimes, 20 years since there was genocide in Kosovo, and a war in Ukraine is still ongoing. The EU has been absolutely vital in stabilizing the continent over that timescale. Croatia and Serbia were involved in a civil war where 20,000 people died within our lifetimes, and Serbia will probably join Croatia as a member of the EU within the next decade, with open borders between he countries and guaranteed rights for minority groups. Cameron's comments were absolutely reasonable.