Your question is wrong
Xianxia, wuxia, etc are always set in a war ridden world, where there is no "universal human right", where strength and skills are worth more than being lawful.
it's pretty impossible to picture a cultivation world with democratic rules and liberal views as our world. imagine a cop trying to arrest a thief only to find out he's stronger than even the strongest official in gov, for sure the cop would just run rather than waste his life for useless justice.
now why the readers tend to be indifferent to genocide ?
If you take cultivation novels as a chemistry exam, you wouldn't give physics answers would you?, And your mind will be in the chemistry mode.
and the authors tend to overlook deaths by euphemising all atrocities. It's the same way a butcher house is seen normal and not a "murderous demon lorde with evil cultivators taking life's".