Kemma,
Imagine you are the enemy and see a Viking Warship moving inland along one of the rivers in your land. The serpent head on the prow, the tail off the stern. Powerfully built warriors from rowing showing no fear of you at all. The fear of Vikings was legendary. Their lightning quick assaults, the brutality of the raids with their axes, painted eyes, cheeks, even teeth in some circumstances.
To show you they do not fear you, they laugh, sing, shout, and dance the oars as if they did not have a care in the world... especially of you. Would this not upset you? Would this not be mocking you and your feeble forces? The warriors welcome death in battle. It is their ticket to be with their God(s). To go to Valhall!!!!! You are nothing to them but targets. They have no problem letting you know this right up front.
Now do you see how it can be taunting?
In Olde Engaland, they had a prayer that went something like this, "God deliver us from the wrath of the Vikings."
The Vikings gave them good reason to be afraid. Imagine your monasteries filled with lambs of their God. Prime raiding targets due to precious metals, drink, food, stock, etc.
It was not unusual to kill all these weak holy men and take everything they could carry on their ship.
Now, to laugh, shout, make a great show of dancing... you would not be bothered by this?
"Better a wolf of Odinn than a lamb of the christian god."
All lambs do is bleat and run, or perish in the jaws of wolves.