I don't think OP is saying anything along the lines of "no one can disagree ever!" I think they are trying to say, if you disagree, that's fine, but disagree politely. You don't need to be overly condescending or rude to disagree with someone.
Attack the argument, not the person making it. Least that's how I interpreted it.
Also this, preferably a staff that doesn't apply scorched earth tactics and suspends a bully and the people defending themselves politely from said bully.