No, you may not. The point was that the man who killed his wife thought he was doing God's work and it was therefore a moral act. It's an extreme example, but it points to the fact that morality is a generalization, not a specific thing with a universal meaning.
Clearly it does nothing of the sort, as he obviously had no legitimate reason to view the act as moral.
The problem is that you can't absolute know very much for absolute certain. This whole world might even be an illusion or simulation. Knowledge is just an objectively true fact. Every view you have about the world is a belief and even true beliefs are still beliefs. So beliefs aren't inherently fallacious. For example the earth being round is knowledge but almost a belief shared by most of the world's population. Knowledge is reality and belief is our perception of it. Being certain about something or thinking that it has lots of evidence doesn't guarantee it is knowledge. People often mistakenly perceive many things of being certain or having lots of evidence when they don't.
The example seems to be too much of a distraction from my point. My bad. It was, in his mind, a moral act. Obviously, the man had some serious mental health issues, but the point is that there is no singular and absolute list of moral and immoral behaviors. What's moral for one person may not be moral for another. For example, I consider greed to be immoral. Other people see greed as a positive. That sort of thing can lead to a lot of tension between groups of people.