The complainant is wrong about his “right” to enter public buildings at will. They have locks for a reason.
Many people and even some Freepers do not understand that there is a difference between “public” and “government”. The government can own a property and then decide to make that property or some part of that property open to anyone. At that point, the property is then “public”. This is essentially public access but owned by the government.
It is also why not all buildings or even all parts of a building are “public”. The city library may be open to the public but the library can and often does restrict access to some locations (storage, office, etc). Those are not public areas. Likewise, a city jail can be pubic access for a very small portion but the rest of the building is not open to the public. Though the building is owned by a public entity (the government of the city) it is not a public building.