A diplomat is someone in the foreign service of their government - i.e. ambassadors and their support workers.
Wikipedia reports breezily that "The high regard for diplomats is also due to most countries' conspicuous selection of diplomats, with regard to their professionality and ability to behave according to a certain etiquette".
The "professionality" of diplomats does not include obeying local laws to which non-diplomats are held perforce. It apparently also includes Machiavellian practices (such as for example Saud bin Nasir Al-Sabah, who allowed his young daughter to lie to a Congressional Human Rights Caucus in an effort to help start the Gulf War).
Former UK ambassador to Uzbekistan, Craig Murray, took a moral stand and refused to countenance involvement with torture. The fact that such whistleblowers are subjected to smear campaigns designed to disgrace them and drum them out of the profession suggests that the reality of life as a diplomat may be radically different from the carefully cultivated appearance.
Diplomats historically have had special privileges and immunities which mean that they are not bound by many laws which are applied to non-diplomats. These extend from the relatively minor such as a lack of limitations on parking or an ability to ignore fines for motoring offences up to and possibly including the ability to violate national laws against theft, child abuse and even rape or murder with impunity. Wikipedia lists numerous crimes carried out by diplomats (homicidal drunk driving in particular).
Sibel Edmonds has testified that large scale joint FBI and DEA sting operations to catch high level international drug trafficking are frequently called off at the last minute by deep political actors with the claim the drug dealers have diplomatic immunity and that the sting has to be canceled to avoid a diplomatic incident.
Office Holders on Wikispooks