One thing that can be easy to forget about an open door policy is that there is still a door. There are so many times that willingness to listen gets misconstrued as agreement. Information is a valuable currency and an open door policy invites it in. However, it is not a “no door policy.” The possibility still exists to close up shop at certain points to avoid negative outcomes.
We are a social species and we need each other in so many ways. However, doors exist because not everyone deserves to get inside or sometimes needs to be removed. Open door is just a predisposition, not a permanent state. Boundaries are healthy things to have. Being inviting and accepting can be counterbalanced by being discerning and observant.
For sure, let the door be open but don’t be afraid to close it when necessary. Access to you and your time should not be frivolously given because then they are not respected. You open the door because you care about others. You close it because you also need to care for yourself.
Shut the front door!
Pete
Huryk Unlimited 
Pete, this may be my favorite one yet.