Allow me to explain the word 'rulecuck':
Let's say you have a favorite board on 8chan, you love it and browse it every day. But there is a problem: other people browse the board too, and sometimes they post things you don't like!
You start to feel angry and jealous, jealous that you are too impotent to make your board exactly the way you'd like it to be. The replies that you get to your posts and threads only confirm your creeping suspicion: this board isn't your hugbox at all, it loves different types of users, and ideas completely different from your own!
Feeling desperate and inferior that you alone could not satisfy/direct the board you post on, you hire an autist with a bigger banhammer than you to do it for you. To come in and absolutely fuck your board for you since you don't have the power to do it yourself.
Who cares if you aren't allowed to have fun on your home board anymore? At least the Moderator is having fun swinging around his banhammer and turning the board into his hugbox!
If the mod tells you he wants to fuck your favorite board, or that he wants to fuck you, the rulecuck will bend over backward and do exactly what the mod says, no questions asked, because he believes the mod to be superior to him. "sure, I was banned" the rulecuck might argue, "but it was for the greater good. I didn't deserve to post that thing anyway."
Rulecuck is the perfect word to describe these people, and they subconsciously know it. That's why the word makes them so irrationally angry.