Jarek Steele, the co-owner of St. Louis's wonderful Left Bank Books (no relation to Seattle's wonderful Left Bank Books), published a blog post about an anonymous letter he received in resopnse to a Black Lives Matter window display in the store:
There was no return address, and it wasn’t signed. It was a very short message on a note card telling us that we had lost a customer. In it, the person said we stoked the flames of enmity between races and promoted division. The person asked us why we insisted upon doing that.
Steele walks a fine line in his open letter, explaining why the store maintains an open conversation about race even as tons of white folks think the matter should be closed forever. He doesn't sarcastically mock the customer, instead concluding that "I want you to know that our door, hearts and arms are open to you and all others always." Steele even adds: "If you do make the switch to Amazon I hope that you’ll keep reading." How many bookstore owners would be that forgiving?
While everyone who's ever worked retail enjoys watching bad customers get what they deserve every now and again, Steele does excellent work walking the fine line between "the customer is always right" and "don't read the comments." His response is earnest, honest, and as full of questions as it is full of answers. You should read the entire letter, because I haven't seen a better example this year of why booksellers are so important as gatekeepers for community conversation.
(Many thanks to @boygobong, who shall henceforth forever be immortalized as the SRoB's very first hot-tipper.)