Sounds like you only read the headline of rule one and not the explanation. You need to click on the rule, because it's a link (that's why the text is blue).

It'll lead you to this which explains what being a party pooper means in this community/context: https://lemmy.dbzer0.com/post/4051762.

Everyone can have a bad day and respond too quickly or with anger. You made a mistake, and broke the one rule of the community. Try to be gracious about it, and you'll be met with grace, I promise.