Do not directly state that an employee is wrong. When saying an employee is wrong flank with relevant proof for your statement. If an employee insists that his or her research has turned out to be something completely opposite to the idea given by you then it would be wise to look up his or her research materials and references. This would help to discover why that misunderstanding occurred in the first place.
Bullying an employee will never earn you respect!
At any circumstance do not yell at the employee or threaten an employee in any way. This is simply not professional and creates fear in employees’ mind. I have personally met people who have yelled at their employees and threatened them with their evaluation report. Would you be that Boss who threatens his or her subordinates? Your employees will hate you for the rest of your life if you follow in this footstep.