This submission has been removed because it involves current events. To keep from discussion of politics, we have a 20-year rule here. You may want to try /r/ask_politics or another current-events focused sub.

Everyone did that. The vikings have a reputation for being exceptionally brutal, but they were by no means alone. I do, however, object to the premise that they did it on religious, ethnic or cultural reasons. ISIS are a religious extremist group masquerading as a political entity. The vikings, on the other hand, were people from present day Scandinavia who went raiding; the word viking derives from the Old Norse víking, used as part of the phrase fara í víking, meaning "to go raiding". They were, by Christian standards, pagan, but there was no religious or cultural motive behind their actions.

A large part of why vikings have such a bad reputation is, as far as I know, quite simple. Unlike the Christian world, the vikings had no literary tradition; they raised runestones, yes, but they did not have the habit of recording events or stories in text. A lot of what we know about the vikings is, because of this reason, from Christian sources, often written by monks. They were not meant to be unbiased.

Two of our main sources on the vikings in the British Isles are the Annals of Ulster and the Anglo-Saxon Chronicle. They were both written by Christians; the former by the Irish and the latter by the Anglo-Saxons. In AD 793, following the first viking raid at the monastery of Lindisfarne, the Anglo-Saxon Chronicle says the following:

In this year fierce, foreboding omens came over the land of the Northumbrians, and the wretched people shook; there were excessive whirlwinds, lightning, and fiery dragons were seen flying in the sky. These signs were followed by great famine, and a little after those, that same year on 6th ides of January, the ravaging of wretched heathen people destroyed God's church at Lindisfarne.

I responded to a similar post a few days ago, here. The final part of the post quite clearly outlines why I think the vikings were pretty damn badass.