Malice or stupidity?

"Never attribute to malice that which can be adequately explained by stupidity" is almost always a bad razor.

If a situation can be more readily modeled by a hypothesis based on malice, than by a hypothesis based on stupidity, it is a dangerous error to insist malice had nothing to do with it.  The correct approach is to evaluate both stupidity and malice separately, then evaluate using common sense — e.g. who benefits from the act, what intentions could the actors have had, et cetera — then pick the hypothesis that fits best.

The other factor at play which gets a lot of people to reject malice as explanation, is that most people conceive of evil only as those acts that would be deemed by a Marvel Cinematic Universe to be evil. That is, they truly believe evil is cartoonishly obvious, so if they can't readily spot evil under those narrowly naïve parameters, to them "it's not evil".

This is absolutely not the case — evil is extremely mundane and takes place all the time at any level of complexity.  Any adult who can't understand this, is functionally a child — who has zero competence and therefore zero business deciding anything for anyone else.

Finally, why not both?  A situation can be the product of simultaneous malice and stupidity.  Yes, a person can be both profoundly stupid and, on top of that, be malicious enough to will his stupidity to bring about evil outcomes.  This is particularly obvious in situations where the perpetrator has access to information that would allow him to make a better decision, yet he still chooses to do something that is detrimental to others.

Evil morons exist.  In fact, they are numerous.   The only reason you aren't dead or under their yoke right now, is that you're lucky only a few evil morons have power over you, and they haven't set their Eyes of Sauron on you yet.  But history is thoroughly littered with the corpses of people who were not that lucky.

Don't discount evil out of a misguided sense of charity.