Because we're currently playing a game of tennis? Where not only is this not the time to be having a back and forth about the nuances of inequality, especially when you're being yelled at by an enraged Williams, but also because tennis has strict time rules between points (this in itself can lead to violations) and it would be unfair to Osaka to allow an extended delay to take place. It's not like he shut her up either. For all intents and purposes, he did take a breath, he did hear her out, and what she said was rude, insulting, disrespectful, and called into question the integrity of the official. That's worth a code violation and I'm not sure how you could argue otherwise.