I think it was more that they would be offended, and not want to bother with the whole negotiating back and forth from such a low starting point and that it's so low that they may think its not a genuine buyer or likely to close.

Just ask the real estate agent before putting an offer in.
I see what you're saying, but if they want to sell, then they have to 'bother' negotiating. If they think your price is too far away, and so you're not genuine, they won't counter-offer, and it'll be up to the OP to make a higher offer.

I've had an agent tell us that they turned down an offer of X last week, so it';s not worth going in any lower than that, but we only went $2500 higher, and they countered at just $1250 above that, so we accepted. It was a final amount well below asking price, and I had expressed my concerns about 'offending' the sellers, to DH... he convinced me to not be worried by it, and just make the offer anyway, and he wa exactly right.

Don't forget that the agent is not *your* agent, they are the seller's agent, and they are not going to give you advice which lowers the possible selling price and therefore their commision.