What to do with people who back out deals

Stuff like this just happens. I responded to a 'For Sale' ad by a member advertising a part plus shipping. I simply asked if he would throw in the shipping for the parts price. Rather than a 'no', or 'I'd rather not', or 'hell no', I got a tirade about me being a cheapskate and how dare I ask such a thing of him. Stuff like this happens.