I would add to your statement

>If you advertise a rule and don't enforce it, you in-effect reward people who transgress the rule... and when why you are surrounded by jerks

that transgressing the rule needs to provide some sort of competitive advantage for the selection to work. Some people may transgress a dress code but I am doubtful that sort of thing will actively help them in the workplace.

It may be in a culture lacking enforcement of minor rules results in more people feeling free to transgress rules that actively benefit them, but that is a second order effect.