It's very unlikely that people just start by being bitter against an industry, but extremely likely that an industry gave people reason to become bitter in time. People tend to start their careers fresh and free of preconceptions, while industries keep carrying their "blemishes" through decades and many generations of people.

You're applying the circular reasoning of "of course I treat you like crap because you have a bad attitude (because I treat you like crap)", while ignoring the part in the bracket.