Political neutrality is defined by the frame, and it includes the fact that facts, themselves, are political, in that some political views are incompatible with certain facts. Therefore, including certain facts in your worldview pushes some political sources out of the frame as being factually incorrect, which is a form of bias.

For example, political views from someone who insists that global warming isn't happening are out-of-frame as being factually incorrect. That means a number of right-wing sites are gone, as the insistence that there is no global warming is more of a right-wing conceit than left-wing.

The alternative is not ignoring anyone, regardless of how lunatic they are, which means you admit known nutcases like whale.to and Natural News into your news diet, and that will give you a very warped view of the world.