Just a guess, though.

We accept that if you're drunk you have diminished responsibility. At least we accept this in some circumstances. If you drive drunk, you have diminished capacity. If you're female and date drunk, you have diminished capacity. I suspect contracts signed while under the influence might be easily voided. No, it's not symmetric--if you're male and date drunk, you are assumed to have full responsibility.

Drunk driving doesn't provoke huge outrage. It just doesn't. Mild outrage, at best. Moral opprobrium, most of the time.

This is cultural.

I personally think that if you intentionally diminish your responsibility, you intentionally assume full responsibility for what you do as a result. If you drink and drive, you should be held responsibility for intentionally hitting whoever you hit. If you drink and date, you're responsible for reducing your capacity. If you intoxicated and sign, you knew you were making your brain not work right and assumed the risks when you lifted the glass or picked up the pill.

The rest is also cultural. Some murders are unremarkable. Gang killings, for instance, don't much matter. Intraracial murders, not an issue. There has to be some trigger to make a murder remarkable these days. You kill a person and then take their innards to decorate your house. You kill a person and he's the main course at a political fundraiser. Those would get attention. Or you put a hot-button topic in the middle. "Death to abortioners!" "I want to kill because I hate people with ___________ skin" or "I hate people who do ______ with their genitals." Killing somebody because they kill animals wouldn't be bad.