Not reacting is different from not noticing.

Choosing not to respond does not mean something went unregistered. People often assume that silence indicates you missed it, and they are frequently wrong. You saw it clearly, weighed the response, and decided the reaction would cost more than the situation was worth.

Let yourself notice fully and respond selectively. Keeping the observation while declining the reaction is a skill, and it is quite different from pretending nothing happened, which does not work for long.