You must have heard of unpleasant behaviour.
An officer started his day by getting nagged by his wife. He went to office and rebuked the employee who work under him and this employee went home and nagged his wife and kids. So this unpleasant behaviour spreads like wild-fire. All these unpleasant happenings can lead to unpleasant scenarios. That’s why we need to be nice and cordial with each other.