Negotiation is part of the process. I expect offers when I list something. I evaluate supply and demand and determine how much I’m willing to move on offers. When buying, I often make polite offers.
Those who are offended by offers are generally:
1. Control freaks.
2. Likely to keep owning the items listed for sale for a long time.
Jerry
PS If you have to announce that you will ignore lowball offers then you aren't very good at ignoring...if fact, you have already acknowledged them before they are made and I bet most of the time you will respond to them, probably with a smart ass remark of your own.