Are Facebook and Twitter protecting Biden?

Donald Trump's favourite news story right now is the one about Joe Biden's son, Hunter, and he will not stop bringing it up. By contrast, most of the news media in the US won't touch it, and Twitter and Facebook both initially put the brakes on related posts. So do they have a good reason? Today on The Signal, we're finding out how seriously you should take the story about Hunter Biden, in the home stretch of the US presidential campaign. Is it getting the treatment it deserves? Featured: Adi Robertson, Senior Reporter, Verge