Not sure what your experiencing but will say for me personally if the offer received is completely ridiculous i myself wont respond but if its at the bottom end of my range will respond with the typical thanks for interest but offer too low. Not saying this what you did but from my experience this is why i wont respond to some.
Like selling my old 72' Triumph Bonneville, all i wanted was $1500 for it and it was a running bike, one offer i got was $300 cash like it was some big favor. When i didn't respond got a few follow up PM's along the same lines about being rude. Well rudeness can go both ways unintentionally im sure.