Matthew 17:20 - He said to them, “Because of your little faith. For truly, I say to you, if you have faith like a grain of mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move, and nothing will be impossible for you.
I get the 'message' - if you believe enough (in fact, even a tiny amount - a mustard seed being tiny) then nothing is impossible but really, what a ridiculous statement and idea for several reasons.
There are lots of people who believe things completely and sincerely even to the point of death. So far I've not noticed any sudden movements of any mountain ranges. Their faith does nothing. All that faith does is motivate people (often to do stupid things) but it doesn't help them accomplish anything. For that you need effort and energy and at that point you are at the limits of human endeavour the same as the rest of us. So what does faith really "do" other than influence your choices? Nothing.
So really what was the point of that scripture? It's blatantly untrue - it is simply a great soundbite that makes no sense if you think about it longer than 2 seconds.
I think a more accurate version would be "if you have enough faith, we can make you do anything". Yes, believe enough and there is nothing that you won't put up with or tolerate or make excuses for. It would take a mountain to move to change your mind if you just believe enough.
It doesn't matter if your church lies, hurts people, rips families apart or covers up child abuse - even a mountain of evidence won't convince someone who has faith.
I guess they can't move mountains but they will be unmoved by mountains of evidence.