Every list has a "Move all cards in this list" menu option. Once filtered by labels, this option remains the same, not affected by the filter. In other words, it will still move all cards, not just filtered ones. (Plus the list shows the total number of cards, it would be nice to see how many fit the filter, right?)
How to do that then? (Imagine like hundreds of cards. Keyboard shortcuts help, but still is pretty mechanical work.)