Fair call, Geoff.
I think that in the case of buying/selling...offers and replies should (mostly) be carried out via pm and what happens on pm...should stay on pm...if you get my drift
If an offer offends....politely turn it down. End of exchange. Simple. Move on.
I don't see the value of venting publically about low-ball offers and bargain hunters when those people did their haggling privately. Just tell 'em they're dreaming and move on.
Just my 2c worth.