is not the same in the UK as in the US, MD is a postgraduate qualification undertaken by Bachelors of Medicine. It can also be the equivalent of a DSc, which is a higher degree than PhD and is awarded for significant contribution to an area of work, generally by the University in which you obtained your first degree.
Generally people who look down their noses walk into walls no matter what their qualification, I think the guy in question was merely miffed at being denied the right to use the title he had worked hard to attain. The assertion that medical doctors are only called doctor out of courtesy is not totally true, some have the required qualifications others don't. Personally I'd rather have a competent one no matter what their level of academic achievement. Speaking as one who has a PhD I can say I've met proportionately more prats with PhDs than without, whether that makes me a prat or not I don't know. I'm sure my colleagues probably have opinions on that matter.