bentley executive called new continental a ` copy ' of bentley flying spur .
luc donckerwolke put remark on designer david woodhouses ' facebook .
side windows of vehicles look similar and both models have chrome trim .
spokesman dismissed criticism and said ` continental is clearly a lincoln '
bentley defended donckerwolke and called car design ` an emotive subject '
general motors told reporters he ` liked the bentley designer 's comment '