Some people don't believe in the cry it out sleep training method here - what's the thinking here?

Cry is the only communication babies have when they are in discomfort. I personally don't believe in cry-it-out-sleep. It just only means that you haven't responded to his discomfort call and let him continue to experience his pain and get exhausted and finally fall asleep. Just compare this with my approach - stomach full with cereal or milk, lullaby in the background and me beside tapping him, as he falls into sleep.