I'm currently re-reading the classic "How to Win Friends and Influence People" by Dale Carnegie, and one of the principles he outlines to win people over to your way of thinking is to "show respect for the other person's opinion. Never say 'you're wrong'." He tells a story from Ben Franklin's autobiography outlining how insolent and opinionated he used to be, to the point that nobody could stand being around him. One day, someone wiser and older pointed this out to him and from that moment, Franklin made it a point to never directly contradict people or positively assert his own opinions. Instead, he'd say things like "I may be wrong. Let's examine the facts." This warmed people up instead of immediately putting them on the defensive and completely changed the success he had in dealing with people. A little tact and diplomacy goes a long way towards persuading others towards your way of thinking. And you never have to say "you're wrong."