Big snag... as highlighted above, despite ICAO's best efforts there are global differences, closer to home you have differing interpretations from UK Civil and Mil ATCO's.... Bottom line, under the heading of Duty of Care a controller should not give an instruction or advice that they know might endanger the aircraft, irrespective of service and class of airspace, unless given with a clear caveat. Not much consolation when you're in the bottom of a smoking crater?
Ultimately (and I know this is a cop-out but) the PILOT is responsible for the safety of the aircraft, so has the final responsibility for terrain clearance. But, as a Controller, if I issue a "direct" clearance I would assume that the level allocated should provide terrain clearance (as I would consider that a vector?)... but if it's "own navigation" then I feel it then becomes the pilot's responsibility (no vector)... anyone?