Being nice to people we know, love, or want is easy.
It is easy to be nice to a person in power, or a successful person.
If a person is nice to strangers, waiters, receptionists, and petrol station attendants, they are nice.
Someone who is nice to you yet rude to a waiter is not a nice person, even if they are nice to you.
If they’re not friendly to a stranger, they’re not nice people.