While I mostly agree, I don't think it's necessarily best to "teach" that, as it does create an exploitable weakness, but I'm not talking about this situation (especially for e.g. daughters). I think my passing take for the moment is people should have their local dispatch #'s memorized. Not for this situation, but there are a lot of other cases where you don't have time to look that up. How many times have off duty officers been pulled over by people impersonating LEO in the news? It's very rare, but not entirely irregular, and for every off duty officer they happen to have pulled over, there is probably a good 200 regular joes. [many of these impersonators don't have malicious intents, but still] I think the best approach is to treat uniformed LEO as LEO only when their behavior, equipment, vehicle, etc. match fully with what you know the department has. If there's any irregularity, then be more aware, and if they are confrontational (pulling you over, etc.) make a quick call to dispatch (non emergency) and state that you want to confirm an officer contact is from their department.

In this case, if rent-a-rambo was legitimately suspicious, he could've informed the officer to wait while he called dispatch to verify his employment. If a real officer didn't comply with that and barreled in (outside of emergency situations or plain sight doctrine) I'm pretty sure it would have serious implications.