As always, it depends. More often than not, the opposite is true, hence the existence of Occam's razor.
Interestingly enough, it doesn't matter in the slightest if some times the excuse is actually true. The intuition is good to have at all times, as Intel's founder Andy Grove used to say - "Only the paranoid survive".
> hence the existence of Occam's razor.
Occam's razor has nothing to do with the topic at hand, you're probably thinking of Hanlon's razor which is a dumb idea 99% of the time, regardless of what actually produced it - stupidity or malice.
Be it flying monkeys, boot lickers, or the abuser themselves. It’s a thought terminating cliche that's designed to stop to critical thinking and minimize the act and reduce the response, making it seem though it were a forgivable mistake instead of a deliberate action.
Because as you said: regardless of malice or stupidity, the harm is real.
Relevant story: my mother grew up in the Soviet Block where they taught her about American Segregation in elementary school. She said she and all her friends immediately dismissed it as made-up propaganda
In that case she was wrong. But I think the intuition is the correct "rule of thumb" to take. By your application of Occam's razor, you would end up believing most propaganda the Soviet education system pushed as long as it offered a simpler explanation. I don't think that's a good intuition to have either.