Is it wrong?

Clearly you did not read what I said.
Cops may not exist in the novel, but there are groups similar to cops.
Murder may be condoned in the novel, but there are spiritual forces that enforce punishment on murderers.
If you're the MC, hope you're an OP MC, because if not, then just killing pests left and right anytime in anyplace will just invite more bigger pests.

In short, kill if you're willing to accept the consequences of your action. Some MC do that, others don't. It's that simple, but of course, sometimes the author forgets to add the consequences of murder in their novels. 

I don't think it's wrong, but more unrealistic. I suffer from the same problem. I liked CN novels so much because they were such a breath of fresh air from JP novel protagonists. I now cannot enjoy JP novels as much as I used to. But it also means that I cannot enjoy some good series as much either. 

They're only protected by their God, the Writer and his Blessing known as Plot Armor. I swear, if the MC encountered ANY actual competent people, they would die not knowing how they befell such a fate. Because those of competence don't need to lift their fingers and just need to put the MC in an un-survivable situation without any chances like such as being able to take control of said energy or being able to wrest control of an artifact away from its user or gain access to a new energy source or give them time to run away. 

you read too much cultivation novels 

It's depend on the novel and the race of mc

beta race mc in cultivation novel will just use jutsu no talk to silence the problem
ALPHA Race Mc in cultivation novel will just stomp the problem just like you step and stomp the ant
beta in modern world setting after got bullied and cannot fight back got isekai-ed
ALPHA in modern world is the one keep low profile and will bully if needed
And so on...... 

it isnt wrong to expect that in a CN novel since they are unrealistic and fantasy based, But that doesn't hold good in other novels.
And plus its scary to think what would happen if the reader got influenced by that train of thought. 

Seems wrong to me. I’m sure some of those people did not deserve to be killed. (´；ω；｀) 

remind me of xue yang from the untamed