1. “If you want to know what a man’s like, take a good look at how he treats his inferiors, not his equals.” – Sirius Black, Order of the Phoenix
This is a complicated one. On one hand, Sirius means well, but ignores his own advice by treating Kreacher terribly, which then leads to his death when the house-elf betrays him.
Also, though we know this is not what Sirius is intending, the idea that anyone is inferior to anyone else is not okay, and certainly not what Harry Potter stands for.
However, as we’ve established, Sirius means well. He has a lot of pureblood nonsense to unlearn. And what he is trying to get at is the same thing most of us think when we see people being horrible to waiters or retail employees.
It’s not about inferiority/superiority; it’s more about privilege and lack of empathy. If someone’s job is to provide people with a service, that does not mean they are a receptacle for rudeness.
There is no licence to bully. It’s about taking notice of how we treat each other as humans. If you witness someone treating another person badly, especially when that person is just doing their job, then there’s the shorthand to tell you they are, simply put, the worst.
Of course, this is something Sirius Black could learn himself, but just because he’s terrible at taking his own advice doesn’t mean we are. If you want to get the measure of a person, look at how they treat others, not just how they treat you.