There is nothing that seven billion people, or even the 300 million people of the United States, can agree on. I feel compelled to state this because I am seeing a bevy of opinions expressed lately in the form "surely we can all agree on X." The Mozilla Foundation argues that "internet health" is one of these things.
I value consensus and decisions made by it are usually the right ones. However, underestimating the stubbornness of people opposed to what seems self-evident to you is never wise. I maintain that today, there are just as many reasons for hostile "tribes"* of people to wage bitter total war against each other as there were in Bronze Age Palestine. In that world it was "my god is mightier than yours and brings rain more reliably"; here and now it is "you don't understand economics, libtard / protectionist." So let us not lose heart when it becomes apparent that not everyone can agree that the earth is round and winters are getting warmer.
*Did you know that the word comes from Latin tribus, or the number three, and originally denoted units of political representation in the Roman Republic? (The word "tribune," tribunus, shares the same origin.)