Why do so many sellers take offense to offers on their listings?

I can’t remember ever “taking offense” to a low offer or being inundated by low offers to the point of irritation.  You list something for sale, you should expect responses.  At least they are looking at the ad.  I might not take an offer on day 2 that I would take after 3 weeks.  It is a simple yes or no, and “thanks for your offer.” I am usually more interested in the quality of the buyer so as to avoid the risk of problems after the sale, which is a practice that has served me well here for over 20 years.

Because they think its fun to be nasty.

I don’t get offended by any offers, instead I respond by stating the lowest price acceptable to me. I am usually in no hurry to sell so i don’t get discouraged by not getting any digs on my sale items, sometimes for months.

This is a great thread. I'm considering making an offer on a pair of speakers. It's good to know how people think.

When I sell a used item, I mark the price as FIRM. My prices are almost always lower than others being currently offered. When somebody lowballs after that, I find it very annoying. It’s hard not to be rude to the low-ballers given those facts.