Indeed it would be a fools errand to try to make it neutral. You probably end up with a tiny list of sources and severely limit the AIs ability.
You can just look at the internal debates happening in Wikipedias list of reliable news sources for how politics quickly seeds into questions of neutral authority and excessive bias.
At least Wikipedia does it in public and ostensibly by the public. I'm skeptical about trusting an opaque organization, who just happens to run the website of the most popular model, to make those choices for us.