I can empathize with deercrazy's experience. Although it's true that its not difficult to say "no", it should also not be difficult to hear "no."
I've had the "I can come look at it a week from Tuesday" (which is not an acceptance of the offer and is really only an offer to kick the tires which is often followed by an offer significantly lower than the offered price). To which I respond "Okay, I'll let you know if it sells before then."
Then, when I sell to a person who unambiguously accepts the offer to sell at the offered price by saying "I'll take it.", I inform the tire-kicker that the item has sold and instead of hearing "Cool, thanks for letting me know.", the person grouses (sometimes to the point of chastising) because because they perceived that they had the right of first refusal. To me, however, they already exercised that right when they refused the offer by not accepting it and instead merely offered to potentially engage in future negotiations.
I understand it's the nature of the business and we should have thick skin but being righteously indignant is fun and free. Sometimes that's all we have in this world. 🤣