>It's polite because it isn't actively negative towards the other person. That's all it takes. Redundancy is irrelevant.
If you believe redundancy is irrelevant, we have different opinions on how people perceive communication.
You: not writing an insult is all it takes to be "polite".
Me: People will perceive the omission of prelude and mea culpa "I'm confused" as "active negativity towards the other person". It doesn't require the literal words "you're an idiot".
So I disagree that simply not insulting is "all it takes". It often takes more than that to not make people act defensive. Lubrication, social grooming, etc.