Walled Gardens - Do walls keep out the bad, or the good? (Ep. 50)

If you're trying to rule a kingdom in the 1400's, good strong walls are a great asset. If you're trying to maximize profits, keeping competition at bay is very helpful. If you're part of a religious organization, chances are someone has (or will) try to build some walls to "protect" it. Is this good, or bad? Links: https://apostlesmailbox.com/ Photo of walled garden by user chris_j_wood at Wikimedia Commons, CC BY-SA 3.0. Unmodified.https://commons.wikimedia.org/wiki/File:Heligan_Walled_Garden.JPG