I like how at first it just shows the headlines/articles. Then, if you want, you can toggle the "show bias" switch.

Have you thought about an option to gamifying it a little bit by letting the user guess which direction the headline leans? And then revealing the direction and the news source.

For example, when the "enable bias guessing" switch is toggled, there's a slider that appears on the bottom of the headline. Or, simpler, just two buttons that say left, right. You can guess all of the headlines on the whole page, then reveal and see how you did.