Rules?  We don't need no stinking rules!  Rules are for those who don't know how to play nice.  If you need a rule, just treat others the way you would like them to treat you.  We're all pretty civilized here.  But remember:

• Everyone is entitled to their own opinion... regardless of how stupid it is.
• Everyone is entitled to be offended by anyone else's opinion.
• Everyone has as much right to their own opinion as everyone else has to be offended by that opinion.
• Everyone has as much right to act like as a-hole as everyone else has to treat them like an a-hole.
• Everyone is entitled to an equal opportunity to say things that make them look stupid and/or ignorant.
• You're not required to agree with everyone... not everyone will agree with you.
• You're not required to like everyone... not everyone will like you.
• The fact that you may feel really, really strongly about your religion/politics/country/pet/etc does not make your opinion of said topic any more right or important than anyone else's.
• The number of people who agree with you is not a good indicator of the validity of your position.
• Whining is not considered socially acceptable behavior.
• Unlike opinions, facts are documented and verifiable.
• Before you form an opinion, make sure that you have enough information to make a judgment.
• Be willing to change your opinion as your information changes.