Targeting Rogue and Opaque Letters Act of 2021 This bill prohibits sending bad faith patent demand letters. A patent demand letter is a written communication claiming that the recipient may be liable for patent infringement. Bad faith means making knowingly false or misleading statements, making claims with reckless disregard for the truth, or omitting information with the intent to deceive. Bad faith representations include false or misleading claims about the sender's right to assert a patent and whether lawsuits have been filed. They also include making written demands for compensation for invalid patents or to demand compensation without identifying the ultimate parent entity of the letter sender. The sender shall have an affirmative defense that it acted in good faith, by proving that its misstatements or omissions were unintentional and that it made an error in spite of procedures to avoid such errors. The bill preempts state laws relating to patent assertion communications. The Federal Trade Commission and state attorneys general may bring actions to enforce these provisions.