The issue here is not about rules placement. An admin had informed you it was against the rules, and instead of changing the sign, you argued with them for half an hour and finally pleaded with the admin to ban you.
Our rules are available in the server's description, in the chat with /rules and /info for our modded servers, as well as our connect page. We're unable to list micro rules in the server description due to the character limit. If an admin, someone devoted to enforcing server rules, says something is against the rules, that's a good indication that it is indeed against the rules.
I'm not sure what your endgame was after telling an admin they'd have to ban you because you weren't willing to remove your sign? I'm sure if you actually put effort into an appeal instead of blaming everyone but yourself for an issue you created, you'd have a great chance at having your ban reduced or even lifted. I hope this information serves you well.