Forum etiquette means maintaining a standard of posting behavior that is acceptable and appropriate. There are certain standards most people expect others to maintain. Some lines must be drawn for the safety of all posting on the forum.
You can disagree with someone's opinions, but calling that person a profane name is a violation of forum etiquette. Keeping it civil is never the wrong thing to do. Posting the same thing over and over again is called scrolling. It is annoying in the extreme. It is entirely unnecessary and makes the poster look immature and childish.
Most forum etiquette involves using the Golden Rule: treat others as you would like to be treated. Behaving as a reasonable adult is always the best course of action. If a poster becomes harassing, obscene or personal, do not retaliate. Instead, cut and paste the offensive post(s) into an e-mail and quickly report it to the moderator or forum administrator.