It's not debatable at all.
We have five senses
Sight
Hearing
Smell
Touch
Taste
That's a rather narrow definition. And wrong. Or at least extremely oversimplified.
All our information about the world is derived from a complex combination of different sensory inputs. Taste, for example, isn't just sensed by the tongue, it's heavily influenced by what we can smell and see as well.
For a cyclist, hearing is part of the complex combination of sensory inputs that give us information about our surroundings, but the problem with hearing is that it is unreliable and often misleading, especially in urban environments. We are not bats. We cannot acquire accurate information about our surroundings from hearing alone.
The sense of proprioception is even more important to cyclists than the sense of sight, and hearing is well down the list - in fact, we can manage to ride a bike perfectly well without it. We can't ride a bike without proprioception.
And anyone who thinks listening to music riding a bike is inherently unsafe would do well to provide some meaningful evidence to back up that claim - ideally something a bit more tangible than 'stands to reason' - otherwise I'll just ignore you the same as I ignore people who tell me it's unsafe to ride a bike without a ****** on my head.