Theatre is probably the only form of free expression, just as theatre is likely to be the only way to escape from the grip of the ego and separate reality.
In theatre you can say and do anything, because you are clearly playing a part and whatever you say and do is not identified with yourself.
In theatre you free yourself from the idea of yourself and you can give space to everything you are, being serious about it, but without the dangers and consequences that derive from being serious about it.