I believe that a person needs to have a certain amount of respect for those who work with and for them. People who respect are respected. A manager who does not respect those he manages will not have the respect of them either. This respect is necessary to keep productivity up.
A certain amount of tact and common sense is probably helpful to make one's attempts at participation effective. Often people have good ideas but express them in annoying or abrasive ways. It's often hard for others to differentiate between the ideas themselves, the presentation of the ideas, and even the person who presents them.
I think that managers have to feel very secure in order to encourage employee participation. Many (or most) fear that they will be shown up by employees, and do not want the employee to threaten or possibly get their jobs.
One of the most difficult is the need to have good information. Employees need to know a great deal about the overall process of production and about the way in which the company works if they are to participate in decision making. Because they often don't it's often easier to be autocratic.