Karl Popper

“Even a brief look into history reveals that majorities can err just like minorities. For instance, 500 years ago most people believed themselves to be the center of the universe (many still do today!) and ostracized anyone who claimed the opposite—like Giordano Bruno. Even just 100 years ago they used to believe that they could support their children’s development by, of all things, giving them a proper caning. The fact that a conviction is shared by 90 percent of the members of society says nothing whatsoever about whether it is reasonable in any way.
At this point we can see what the particular strength of the modern, open society is. For it protects minority positions not only because freedom of opinion constitutes a precious asset under the rule of law, but also because the amicably adverse conflict of positions is the essential driving force of societal progress. This is where the slogan “diversity instead of uniformity” becomes valid, for it is true: it is only because we are different that we can learn from each other. If we were always in complete agreement, we wouldn’t have much to say to each other. We would have no counterpart that could correct us, but would instead keep affirming each other in our prejudice, which would bring societal development to a halt.”
Michael Schmidt-Salomon, ‘Die Grenzen der Toleranz – Warum wir die offene Gesellschaft verteidigen müssen’. (Translation: Janosch Rydzy) - see link in comment...