If Trump says something about a company, that can make the company's stock fall quickly. Businesses shouldn't have to live in fear that Trump will defame them if he doesn't like something that they are doing. They should exercise their right of free speech and tell the truth about their companies.
Donald Trump has a reputation for saying whatever comes to his mind, often without thinking of the people who will believe him and the consequences his words will have. Fact checking him and calling him out for incorrect statements can force him to be more disciplined with his words. This is a very important skill because of the numerous international relationships Donald Trump is now responsible for keeping as president.
If Mr. Trump lies, people should call him out. However, instead of calling an untruth a lie they should stick to calling them untruths, miss-characterizations or the like. Calling something a lie comes with it a level of judgment that is not healthy or productive. Yes, call out the things that are not true, but don't label them as lies.
Yes, people should call out Donald Trump's lies. It's a responsibility of citizens and the press to call out their leaders for lies or misdeeds. In the case of Donald Trump, it is particularly important for at least two reasons. First, Trump seems to tell a great number of lies and often brushes them off or dares people to challenge him. Secondly, and possibly more significantly, there seems to be a large group of citizens who choose to believe only the best in Trump and refuse to acknowledge his lies and misdeeds. Others are going to have to speak louder to get the message across. Otherwise, our country and others could be in serious trouble.