The Vanguard bit is irrelevant. With weapons of a range of 7,000 miles they hardly need to get close to Argentina to be considered a threat - not that in a million years they would ever be used as an offensive weapon.
The Argentines are just deluded. Rob Liddle wrote a good piece in the Times about it yesterday basically summising that no american country can ever make complaints about colonialism seeing as the countries that now make up the continent all have an origin as colonies of european powers, the north as much as the south and central bits - and perhaps they still suffer from the latin jealousy complex because the countries that speak English have done a lot better than those that don't.