Universal Ettiquette- what can be agreed upon regardless of culture?

I understand that somethings may be considered ethnocentric (ie painting your house Magenta, parking on your front lawn, genital mutilation, gluten, and ceasar haircuts)...but is there a list of agreed upon rules that can be filtered by the deepest of southern pastor, the hairiest of arm pit femminazi, the stepfordiest of wife, the foreignistiest of eyes, or the bawiest of baws?

Earth rule #1: "On Earth, people who are on an elevator must be able to exit the elevator, before "ANYONE" should try to get on"

The elevator rule.....whom does it oppress, whom does the rule demeen.....Can we agree as a planet that this rule is 'Just' regardless? If not wat is one rule that humanity as a whole can agree upon without someone's burqua-stock-N'Nuts getting in a bunch?