This gym teacher's actions are not motivated by hypocrisy, but hopelessness.
A lot of older people feel it's too late to improve themselves, but that they can still work to improve people younger than them, like Chip (played by Jim Carrey) in The Cable Guy:
"No. It's too late for me, but there are a lot of little cable boys and girls out there who STILL have a chance! Don't you understand, Steven? Somebody has to kill the babysitter."
https://www.imdb.com/title/tt0115798/quotes/?ref_=tt_trv_qu
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