No, but it's pretty naive to think that the 5 people you've met are representative of an entire culture.
You have to examine where and how you met them and ask yourself whether those circumstances are normal for all of Scandinavia.
For example, I've met a few Greek people, but I don't think that all Greek people are well spoken, well educated, fun loving, partying, attractive young women, because I know that the Greek people I met at University aren't representative of the entire country.
Not everyone in Greece has the opportunity or desire to study in Britain and the Greeks I met are more likely to be a certain type of person that isn't restricted by nationality, nor representatives of their nationality.
Likewise, I would be a fool for thinking everyone in Sudan is a pot smoking, hip-hop loving, video game playing dude and it would be a great holiday destination just because of my experience with some Sudanese people (who were also the children of high ranking Diplomats and similar "elite classes", hence them studying in the UK).
So, these 5 Scandinavian people, where did you meet them and what demographic did they fit into? If you met them in the UK and they were students, then not only would they not be representatives of the entire population and age groups, but they may also not have been behaving normally as they would do in their own countries. They could have been playing up the obsession with Vikings because it's what you expected them to talk about, or because it's a taking point and an easy conversation to have in a foreign land.
You have to also consider that they could have been taking the piss and only pretending to be obsessed with Vikings because it's a stupid stereotype that certain people will fall for because they are too eager to believe it without thinking (like this one Cuban guy I knew who would play up the Communism, Castro idolatry and revolutionist spiel to certain people, even though he wasn't like that at all).
