There's no evidence that a diet high in olive oil increases obesity or all-cause mortality.
GP's point is that calories coming from a "healthy" source doesn't mean they don't count. Drenching one's salad in olive oil rather than canola oil won't help someone lose weight, nor will switching from soda to a fruit juice with the same amount of sugar in it (ancillary benefits of e.g. vitamins notwithstanding)