Isolated religious communities were easy prey for the Vikings. The lure of gold and silver ornaments in monasteries, nunneries and churches was irresistible to the Norsemen. Yet many Vikings professed to be Christian. So why did they not respect other Christians?
In the eleventh century many of the Danish and Norwegian Vikings had embraced Christianity. So it is difficult for us to understand that men, who came from so-called Christian countries, albeit fledgling ones, could be so bestial and cruel to brother and sister Christians in other countries. To comprehend this we must remember two salient facts. Firstly, the pagan Gods so recently worshipped by the Vikings existed to serve the people, not the other way round. Yes, they required sacrifices, and quite often substantial ones, but if a God did not perform then the Vikings would change their allegiance to another God. Thus, for example, if a harvest was poor, a person might decide that Freja had failed them and therefore they would try a different God for next year.
Secondly, the Christian faith has a code of morality which followers must embrace. This concept was totally foreign to the new believers, their previous Gods made no such demands. This code was to a large extent ignored as an inconvenience to them when other priorities such as satisfying greed, lust or hunger took over. Even King Sweyn of Denmark, a professed Christian who built churches in his own country including the one in Roskilde where he is buried, had no qualms about plundering English religious establishments and killing monks when it was a matter of political expediency.