But in doing so they have become what they hated. They are now actively helping maintain and rooting for the stupid rule instead of fighting against it.
I see no compromise of principle in people who maintain and enforce stupid rules they disagree with. The most honest response is to argue for and support sensible rules, not to turn a blind eye.
I'm not saying that I think it is a good idea to follow bad rules - but people who disagree with rules and follow them anyway on solid moral footing and should reasonably expect others to do the same.
it's been my experience that people generally don't follow rules they disagree with, unless they are afraid of the consequences. As such, seeing someone breaking the rule who is also someone in power over them with ability to enforce the rule can be especially galling.
That said, if it's true that metro passengers have effectively been harassed and abused and arrested for years over this no-eating rule, then I can see how it would be more offensive to see an employee breaking it publicly, and this person's reaction makes more sense to me.