If that was the parents' point, then why didn't he say so?
Not all door can be locked in real life (indoor doors), but if they look the same, I agree they should behave the same. That doesn't mean that all locked doors need to have a key that opens it in the game. It's perfectly okay to have a street of locked houses where only one house (the one that's part of the script) has a matching key.
Also, neither of us were talking about blocking/non-blocking doors; that would obviously be inconsistant physical behaviour.
IMHO, a locked door that has no key in the game, is perfectly consistant. The problem is not so much the individual door, but rather that the world (i.e. the "room") behind the door should be modeled as well. Would you rather have a cheat like F.E.A.R., where the room is filled with boxes? How realistic is it to have a room that is filled upto the doorway with impossible to move boxes? It's trading a minor inconsistancy (a locked door for which you can't obtain the key for a variety of reasons) for a major inconsistancy (a street with all box-filled houses).
If the demand is for every room behind every door to be accessible and fully modelled (no silly cheats), then that practically prohibits large scale city scenes, simpy because of the practical limitations of developing such a world.