I tend to cut movies a lot of slack, since I believe that the more sophisticated our movie-making abilities become the less people tend to use their imaginations. I bought a used VHS copy of "The Norseman," and watching it as an adult I actually enjoyed it. Sure, it's not a well-made movie, but it's a sad fact of life that often the smarter we get, the more jaded we get. I suspect the reason one viewer enjoyed the movie at ten and hated it as an adult is that watching it through eyes of childlike wonder he was able to suspend disbelief and see the movie's real meaning.
Besides, what's so "laughably stupid" about the plot, a conflict between Vikings and Native Americans? There is pretty good evidence that the Vikings were in North America; ever hear of Vinland? And as for the "black Viking," that was probably a pandering to '70s social consciousness; but still, could they not have picked up an African man in their travels? Everyone has their tastes, but I found this movie's theme unique and intriguing.