Allan Ross, where did you learn to read?

In the first place, the phrase "giving a voice to half the American electorate" does not mean the same thing as "half the American electorate reads Breitbart". Instead, the phrase "giving a voice to half the American electorate" means that Breitbart broadcasts (gives voice to) the views of half the electorate, which is about right, given that at least half of the electorate has doubts about the accuracy of the mainstream media. I mean seriously, half of the left wing pundits on MSNBC and PBS expressed doubts about the accuracy of the mainstream media in the days after this election, in mea culpas, over expectations of polling.

In the second place, even if we take your interpretation, sorry, but only about a hundred million voters vote in the typical American election, so about fifty million actually is about half of about a hundred million.