Okay, so I'm gonna be blunt. We don't have to write out every single thing 100%. Our rules are not an all-encompassing list of every bad or less-than-awesome thing a person could do on the internet. Expecting them to be is entirely ridiculous - we have better things to do than enumerate every horrible thing, so we have to do trust that our users have some awareness of what is and is not acceptable.
You are correct that democracy is not the be-all and end-all. We use democratic principles when it makes sense - for example, asking about how people want to see certain pages categorized or formatted. However, there are topics that aren't up for discussion. For example, if literally 95% of people voted to allow racist content we still wouldn't allow it because we have some basic principles. You are correct that we can 'just do stuff' for the most part so long as we uphold Fandom ToS and Community Guidelines. That's how things work the world over, barring the 'Fandom ToS' bits. That's not to say we don't try to be fair, but we're human and there's not some perfect cosmic ideal or law we follow.
So, why did we do that here? Because it's not an appropriate question for this board. You were asking if it's acceptable for a character who is in all ways but physical an adult to have relations with another character who is a child, and you did it as a poll where two options (yes and no) were presented equally. That legitimizes the stance that this is in some way acceptable, which in a soft way normalizes some really awful behavior. If you'd made a post (not a poll) like "I wish they'd stop having this kind of content in shows" that's an entirely different kind of post with a very different tone.
To give another example, let's say someone made a poll that said "Is it okay for a superhero to only fight villains of a certain race?' with just the answers yes and no. Presenting both of those options neutrally makes it seem like one of these things is okay. I can show that this is true because 42% of people said yes to your poll and I'm sure most of them are not pedos. That's how people work - if you present two options without elaborating they will assume they are roughly equivalent unless they have background knowledge or have thought or learned about this issue previously.
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I'm going to give you the benefit of the doubt and assume you are not a pedophile. You're probably just someone who didn't know better and framed this in a weird way, which is why we deleted your post and talked to you about this. It's also why I'm spending my time here explaining this to you. That's very generous in my opinion, I think most places they would have seen it as just you talking about some pedo-bait topic and have banned you outright without giving it any further thought, and I hope you realize the genuine good will and effort being put in here if you respond to this.
In summary - consider how you frame things. You didn't hurt someone's fee-fees and get a post deleted because you made a staff member upset, you had a post deleted because it looked like you were trying to legitimize some pretty gross stuff. The effort put in to try to explain the issue to you on your wall and here is way above and beyond, and I don't love seeing users throwing a fit about how this is some anti-democracy tyranny zone when we're doing way more than we need to.