The centrists are still there, you just don't here about them because reasonable, compromised views between groups don't get people to click links as much as "MAN DOES SEXIST THING AND OFFENDS ALL WOMEN" or "WOMEN DO BIZZARE THING THAT'S TANGENTIALLY RELATED TO THEIR IDEALS AND MAKE A VIRAL VIDEO OUT OF IT." Internet news doesn't lend itself to middle of the road viewpoints (or voting systems like voat's or reddit's), so they just get drowned out.