For many years I have listened to people say that we need an open mind. Quite often they analogize their idea to that of a parachute: if your chute ain't open, it ain't no good.
Contained in that thought is an insipient lie.
Consider: If a parachute is always open, it is useless as a means to leave a perfectly good airplane in flight, in order to get to the ground safely.
Ask any pilot, and they will verify that a parachute must be packed a certain way, in order for it to operate properly. If it ain't packed right, you get the shroud lines tangled, and the chute fails.
If the chute is not packed, and you jump out of a perfectly good airplane while in flight, the shroud will not open, and it is my understanding, you will be the first person on the ground.
Getting back to the mind needing to be open, the analogy still holds true: if your mind is "open" all the time, it will necessarily take in stuff that is harmful.
Proponents of the open mind ideal, have one goal in mind; to change people's minds, and bring others to believe the same way they do.
On second thought, I am convinced that keeping an open mind at all times is worse than waterboarding.