Because it's in reference to "honor killings" that still take place in certain cultures.
Familial violence against women, unfortunately, happens in all cultures. It gets called "honor killing" when it happens in a few of them.
Cultures where domestic violence is a crime are NOT the same as cultures where domestic violence is encouraged.
Cultures that have honor killings are the latter.
No, it is not socially acceptable (or even expected) to kill family members because they've done something which brings shame to the family in all cultures.
It's not "expected" (or "legal") anywhere. That's my point. Family annihilators exist globally and we imagine other societies approve of them.