You're just making up the rules of morality now to find something good in the situation. Which shows how flexible morality is. The norse viewed it as an honorable death, but the reality is they were trying to kill people and got killed. There isn't much "honor" (from our moral perspective) in what they were doing or wanted. We aren't talking about a burglar in their home and they died defending their family. We are talking about being the burglar and getting killed. If somebody broke into your house with the intent to kill you, steal your goods, and rape your family, and you shot them, would you be immoral for doing so? and would you say that burglar died an honorable death? And also which innate objective moral systems that we all share make the answer for the first two answers correct?
Which leads to the question, what is this objective moral code that we all agree on, but refuse to obey? It can't even be something as simple as "do to others as you want done to yourself" because as has been shown, even that will lead to problems depending on the culture.
As for the rape aspect, that is for one moving the goal posts. Now that we've shown that murder can be thrown into the golden rule and still work, we'll just say having one's daughters raped crosses that moral line. Except again, the bible gives us examples of that not being such a big deal either. Exodus 21:7 deals with the proper way to sell your daughter to men that are allowed to use her as a sex slave. Of course this in in the era of extreme mysogeny where arranged marriage and all sorts of disgusting things were the norm. But that kind of goes to the point doesn't it, in their culture selling your daughter to men who may force them to marry their sons was perfectly ok, and moral. They didn't ignore some moral sense that told them how horrible it would be for their daughter, they just bought and sold women.
When a man sells his daughter as a slave, she will not be freed at the end of six years as the men are. If she does not please the man who bought her, he may allow her to be bought back again. But he is not allowed to sell her to foreigners, since he is the one who broke the contract with her. And if the slave girl's owner arranges for her to marry his son, he may no longer treat her as a slave girl, but he must treat her as his daughter. If he himself marries her and then takes another wife, he may not reduce her food or clothing or fail to sleep with her as his wife. If he fails in any of these three ways, she may leave as a free woman without making any payment