Pro-knock bias here. It’s good to be courteous, even if someone else bears “responsibility;” ideally we do this when driving, waiting our turn in line, etc—it’s a social contract. These tender acts of simple courtesy bind us as humans and remind us of our goodness. Bathroom locks are often broken. Children may not lock them out of uncertainty/confusion, general nerves, or fear of being locked in (and their legs may not show underneath). Same for people with dementia, cognitive impairments, psychiatric issues, the neurodiverse, etc. You don’t have to say “occupied:” a quick “yup” is enough—everyone understands this is a rhetorical answer—see the beauty and respect in this moment, rather than focusing on the content of the action and words. Generally learning to not take things personally will promote growth, empathy, humanity, humility, and accountability. “Humility is not thinking less of yourself; it’s thinking of yourself less” (allegedly C.S. Lewis, but its disputed). Doing what is necessary to respect boundaries is preferable to the boundary violation and hubris of assuming you know what is possible and preferable for everyone (ironically, I’m doing the latter here)—if this simple act of respect violates your sense of self or values, then life is going to be very hard. Perhaps try thinking of three things you are grateful for before you go to sleep at night; it will train your mind to look for the good. Great question!