I think the "you can't freeze bananas" view dates back to the 50's when freezers were a lot less efficient. Certainly my Mum subscribes to it. They do go brown quite quickly once they come out of the freezer (the bananas, not Mums)
I peel and chop bananas then freeze the pieces. Thrown into a liquidizer with a couple of ice cubes, sugar, rum , milk, lime juice and yoghourt - hey presto the milk shake equivalent of banana daiquiri and thick enough to stand a straw in