The only arguments against joining the EU I've heard so far from staunchly anti-EU people are variations of "we'll be ruled from Brussels", "the EU will take all our money", "we'll be flooded with foreigners" and "we'll lose our culture".

The response to these claims:

We won't be ruled any more from Brussels than France, Spain or Hungary is. All these countries have their own methods and unique sets of laws you have to familiarise yourself with before moving there. The EU won't take our money any more than any other member; it's a mutually beneficial transaction. We're already a part of the EEA and Schengen so anyone in the EU has the right to live and work in Norway, just as Norwegians enjoy the same rights. I've visited most countries in the EU, and can't say I got the impression that any of their unique cultures were under threat. We stayed in normal residential areas, far from the touristy parts of town, and could clearly see the unique characteristics of each place we went to.