Even the argument that cyclists without lights are reasonably visible in well lit urban areas is only true if you happen to be looking directly at them. In a driver's peripheral vision and, crucially (especially for lorry drivers), in the rearview mirrors, it's not at all true. The "pedestrian" comparison falls down here, since it's not usual to find a pedestrian who needs to be seen in your rearview mirrors. Besides, I don't see what's so difficult about buying a couple of LED lights and sticking one on each end of your bike. It's hardly a massive expenditure or a huge amount of effort, and given that, I don't understand why all this effort is going into defending unlit cyclists.