There has been varying discussions regarding the changes to the murder laws in England and Wales. Most spout the familiar line and regurgitate the usual reactionary myths about domestic violence. But to reiterate, the reason more men than women get done for domestic violence is that the vast bulk of domestic violence is by men against women.
As I understand the criminal law is based on the assumption that a person has free will in deciding what actions they take: they may decide to break the speed limit, sell cocaine or kill their wife. This is the only basis on which someone can be justifiably be punished for something.