I agree that the problem is that filtering out the truth is hard, but creating an arbiter of truth also has many other problems. Whoever gets control over the arbiter can shape the truth top their liking. Right now what we view as the truth as a society is shaped by the sum of everyone speaking out, but if you think you know better then you can simply override it. Others might disagree, but you're still encouraged to think for yourself rather than rely on someone else.