I had this discussion with my mother (who went to school in the early 70s) when I entered school. Her position boiled down to it being reasonable for her to drink because it was legal, and unreasonable for me to drink simply because it was illegal. Now, I don't equate legality to morality, in no small part because she didn't raise me to do that. When pressed to actually explain her disapproval, she relented and admitted that her position was hypocritical.
Hypocrisy isn't about changing your mind. It is about holding yourself to a different standard.