Think of it this way. The Rules are a standard of conduct. They're good guidelines for etiquette and for protecting your interests. They leave lots of room for your own judgment and discretion as to how you are going to construe and apply the rules on a case by case basis.
We take themseriously because if you are going to call yourself a Satanist, how you present yourself reflects on the movement, on the Church of Satan
, and on other Satanists. So, the rules are there to say, "Here is the kind of behavior we want to be known for."
Also, we take them seriously because the underlying message is, "Don't be an asshat", and we don't like asshats.