Were Vikings really dirty and ultraviolent brutes?

One-sided representations of Vikings do not paint the full picture of their reality in the Viking Age. 

On the one hand, it would be inaccurate to deny the aggression, pillage, and destruction associated with Viking campaigns.

On the other, it is also important to note that Vikings were not only invaders and conquerors but also migrants. After their campaign ended, a lot of them stayed in the locations that were targeted.

Furthermore, their relationship with the local population was often complicated – there was often intermarriage, and some Vikings converted to Christianity. The Viking era was characterized by both immigration and assimilation.

At the same time, Vikings often kept their traditions, habits, and Norse names.

Unreliable sources

The barbarity and ghastly hygiene attributed to Vikings were often misreported. Modern experts believe that early historians accepted sources about Vikings that are now regarded as unreliable.

Furthermore, surviving accounts of Viking activity were often written by churchmen. As the Vikings often attacked monasteries due to their wealth, this was the cause of an obvious bias and antagonism against them, contributing to the current image of Viking atrocities. 

One such example is the work of German 11th-century chronicler Adam of Bremen. Another example can be found in the work of Alcuin of York.
Here's an extract from his description of Viking raids on Ireland and Britain:

"Never before has such terror appeared in Britain as we have now suffered from a pagan race… The heathens poured out the blood of saints around the altar and trampled on the bodies of saints in the temple of God, like dung in the streets." 

Adam of Bremen,  Alcuin of York, and others are responsible for overemphasizing the barbarity and uncleanliness of the Vikings.