Most of our light pollution is caused by "carelessness". We put on way more lights than we reasonably need, and we put on the wrong kinds that are more confusing to wildlife.
Aliens might not do that. Their cities might be fairly dark at night.
Aliens might not even use light or radio based vision. They could be like bats and use echo location.
You are also assuming "intelligent life", and that it is sufficiently advanced to have created cities and some form of light bulb. (this could include a lantern). Without that you have to rely on other signs of life.
I'm not sure you've been following the conversation... I'm not wondering how we can find life, I said looking for city lights at night is a bad way to look for life.
The night-side view is merely looking for surface-generated radiation with less interference from external radiation.