Warning: Contains spoilers for New Mutants #21.
The mutants of roster is the greatest in X-Men history, they are still running into some major moral issues that do not paint them in the best light.
the Brood has taken over Thor and other powerful heroes. It's clear from their depiction that they are bad news.
In New Mutants #21, the team is doing a bit of "team building" in outer space, clearing space nudibranches from an area when the Brood appear. The aliens attack Warpath and the rest of the group, and the battle begins. Fighting the Brood is a common activity for the X-Men, so this is not entirely out of the ordinary. However, their fight against - and killing - the Brood has become a more complicated endeavor than before. The Brood display human-level intelligence often, and due to their hive mind are able to feel human emotions as well. Further, the group of Brood the heroes are fighting against is seceding from the larger group - a pretty emotionally complex action. Others have pointed out that Krakoa can cause a lack of empathy among mutants towards those outside of mutantkind.
The specific issue with the mutants killing the Brood is simple: the heaviest rule of Krakoa is "murder no man." The reason this law is the most severe on Krakoa is that mutants can be resurrected and it's morally indefensible to take the lives of mortal beings. While the rule has been occasionally suspended for emergencies, the core of the rule exists due to the power imbalance between mortals and immortals. The mutants going after the Brood as strongly as they did seems to imply that, while the Brood can die and aren't immortal, that "murder no man" rule simply doesn't apply to the Brood. The rule seems to only apply to mortal creatures that look and think like mutants do (or are, at the bare minimum, humanoid). There are already inequalities on Krakoa Shadow King is exploiting, and this division between humanoids and non-humanoids could spell more trouble.
For decades, humans have killed mutants because they are different. It's a core feature of the X-Men stories and mythos and a driving force behind many of their actions, so the "kill no man" law makes perfect sense as they work towards peace. However, it would seem that that rule does not apply to to other beings. Could it be that this rule is a "humans only" situation? Or perhaps those who look more like mutants than the Brood do. Further, there are some hints that Krakoa may not actually be paradise, so perhaps this new rule being broken is only the tip of the iceberg.
New Mutants #21 is available now.
