Which of the following is NOT a violation of federal antitrust laws?

Refusing to do business with a competitor deemed unethical is indeed not a violation of federal antitrust laws. Antitrust laws are designed to promote fair competition and prevent monopolistic behaviors, but they do not restrict a business's right to choose who they want to work with or to make decisions based on ethical considerations.

This means that if a business decides not to engage with another competitor due to ethical concerns—such as differences in business practices, values, or customer treatment—they are exercising their own discretion and judgment, which is permissible under antitrust regulations.

In contrast, the other options involve actions that may lead to anti-competitive behavior or collusion among competitors, such as discussing commission rates or marketing strategies, which could reduce competition and harm consumers. Therefore, the correct choice highlights a legitimate business practice that aligns with personal ethics and does not infringe upon antitrust laws.