There are some obvious bad calls that I think most football fans can look at and realize that was a bad call. Some of them in the past have been due to the rules being poorly written. Honestly the competition committee's poor writing to the rules has caused far more problems in the past than the refs.
However the PI wasn't one of them. That was a simple bad no call by the officials.
That said I think those are the exception to the rule. If calls that bad were every day things, we wouldn't be talking about it.