The consequences of his action are certainly a big problem for the Vampires. But the person that caused it is not nearly as big a problem. He is around the strength of a new origin god so he isn't that dangerous.
But there are others who believe that he should not be excused because he is a weak threat. They believe he is too strange to be spared. They believe so because there are a lot of things they don't know about him and what they do know about him is unsettling.
First, he broke off his connection with the demon god. They as primogenitors know how difficult it is to achieve that. It is not even possible by their knowledge. Or in this case, it isn't supposed to be possible.