Crocker's Rules, named after wikipedia:Lee Daniel Crocker, are a rationality-enhancing technique.
By declaring commitment to Crocker's Rules, one authorizes other debaters to optimize their messages for information, even when this entails that emotional feelings will be disregarded. The underlying assumption is that rudeness is sometimes necessary for effective conveyance of information, if only to signal a lack of patience or tolerance: after all, knowing whether the speaker is becoming angry or despondent is useful Bayesian evidence.
Thus, one who has committed to these rules largely gives up the right to complain about emotional provocation, flaming, abuse and other violations of etiquette in the interest of effective debate.
In contrast to radical honesty, Crocker's Rules encourage being tactful with anyone who hasn't specifically accepted them. This follows the general principle of being "liberal in what you accept and conservative in what you send".