To me it must have been someone who obviously had little idea of how things work on websites such as this one. That said I have never actually done business with MM but have on occasion called with questions or looking for parts and have found them to be more helpful than most others I have had questions or requests for in the past. I would not hesitate to do business with them in the future based upon their willingness to dig in and try help someone in need.
Based upon the harsh response to a simple slip up I don't think it would be worth the risk of doing business with the accuser for fear of further reprisal if things didn't go 1000% perfect. JMHO.