We should never speak badly of people that we have allowed to behave badly.
We cannot control other people’s behavior, but we can take charge of our own.
Practice: Identify something, anything, that you consider bad behavior. The size of the offense doesn’t matter, nor does whether anyone agrees with you.
Next identify what you do that permits the behavior you dislike. Remaining at the counter while a clerk chats on the phone comes to mind, but you no doubt have a list of your own.
Moving at whatever rate is right for you, change your behavior. Leave already, or ask for the manager, or shop elsewhere. Or. . .
Changing your own behavior is more demanding than bad-mouthing another’s. And far more effective.