I've seen this interesting behavior in other contexts. There is a stupid rule that nobody likes. People make an effort to follow it despite hating it. When they see someone breaking the rule they feel that it's very unfair because of the effort they are making, so they report it to make it fairer. Either everyone should follow the rule or it shouldn't exist.
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.
We all follow rules we don't agree with; that is part of the social contract. Selective enforcement of rules is one of the biggest threats to those who behave lawfully.
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.
>We all follow rules we don't agree with; that is part of the social contract
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.
Narcing on your neighbor for building an unpermitted shed because you feel like a chump for pulling permits when the reality is you both could have gotten away without permits is very different from narcing on somebody who is only getting away with it because they have some special status with the organization responsible for the rule.
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.