They get paid to deal with customers. It's their job, end of story.

The reason people say it's exhausting to "be nice" constantly is specifically because of people like you. You've made up your mind on something that's completely outlandish and unfair, but you're going to attack him for being "unkind" because he doesn't agree with you.

Stop acting like that and maybe more of these "blunt" people would stop being so damned blunt to you.