Thank you for your patience as I put together my response. You are correct that you did no wrong with your cactus farming and llama claim/pushing, but it was other actions over the course of the two weeks since you've arrived that resulted in a ban. You were warned by the signs at spawn with the rules of our server and also both officially and via messages to not grief other player builds as you went along.
A few examples are:
Griefing other player builds with blocks placed by you:
You killed not one, not two, but three other player's pets over the course of the past two weeks as well.
I would like you to take a moment to review the rules of our servers at http://www.redditpublic.com/wiki/Rules.
The first time offense ban is 7 days from the moment of banning, so you may make a post on the 3rd of December to get unbanned, letting us know that you understand and have read the rules and will not repeat the offense. If you repeat the offense, it will result in a longer ban.
Please remember you may not evade the ban by using alts, or it will result into a longer ban time.
If you have any questions, please let us know.