I'm nuts? That's what governments are based on. It's no surprise that a group operating outside existing legal structures will find itself in need of lethal force. If you were running a little village and someone came to take all your food, essentially condemning your whole family, force may be the only response.

So it's quite understandable that a criminal organization might need to use force when someone threatens their safety. This happened for instance with the Silk Road, when someone blackmailed them. (Now, the SR shouldn't have allowed themselves into that position in the first place, but that aside). It's a "necessary" understandable case - if not taken care of, dozens or hundreds of people could be condemned.

Contrast with these cartels, which hijack passenger buses, then torture and rape for fun. There's no necessity there.

Do you not see the distinction?

That is its own necessity. They are at a place, in terms of their environment, character, moral mindset, and predilections, that torturing and raping for fun is preferable (controlling for other factors).

This kind of behavior has had a strong appeal throughout history to many of those with the strength to carry it out without any real risk to themselves. See Jack London's "The Sea Wolf" for a great portrayal of the conflict between this mindset and our own. It's player-killing in video games in the real world and the only effective way to respond is with greater force.