Umm... well, let's hear him out.
The practice of marrying more women allowed the eligible bachelorettes to have high expectations about their future husbands, and impoverished or underprivileged men didn’t fit the criteria.So it's the poorer, less powerful men who need women.
In order to raise their chances of getting married, young Viking men joined the raids, hoping to enrich themselves. Sometimes, they even kidnapped Celtic women on their warrior “voyages.”"Sometimes" to such a degree that Iceland's population descends, according to recent genetic studies, from "Norse men and Celtic women."
Well, I do keep reading arguments, both by men's rights activists and certain kinds feminists, that marriage is a form of slavery...
No, look, this is simple. Slaves were one of the main things raiders of this era -- not merely Vikings -- wanted. Unlike the slavery we think of in American history, however, pre-modern and ancient slavers -- like ISIS today -- wanted female slaves. Males were typically killed, although men caught young enough were often castrated and sold as eunuchs in certain parts of the world (the Muslims in Spain did a huge trade here).
One of the underappreciated qualities of the Western European High Middle Ages is that it eliminated chattel slavery, though not until after the Viking Age (but around 1300, even in fringes of Medieval Europe like the Scottish Highlands). Unfree labor persisted, as for example in serfdom, although that too diminished as the feudal system began to give way to town-based market economies over the period. The driving force wasn't economics, though, it was Catholic moral arguments against enslaving fellow children of God. The idea was that there was a pure equality at work among all our fellow human beings: God had made each of our souls, after all, and loved them each equally. It therefore could not be moral to enslave another.
Chattel slavery was reintroduced in the Renaissance, as Portuguese sailors captured and discovered trade routes to Africa that allowed them new opportunities for rich trade as long as they were willing to trade slaves on one leg of the voyage. The whole apparatus of color-conscious racism was built out of a desire to avoid the Medieval arguments against enslaving fellow children of God by trying to create a middle category between humans and animals (who could of course be owned).
But if we are talking about the Viking Age, we're talking about the pre-Christian period in the north. The later Catholic arguments had not been developed and wouldn't have been persuasive to a non-Christian people in any case. They were still doing what the Greeks had done at Troy, and as ISIS does today: take what your right hand can control, and rule it.

