Hmm, the more I read about it the more I can understand the position of you company. This is not about the porn CD, it`s - from the point of your company - only about your behavior. They want to be sure that you have "just" overreacted a little bit and are not a complete nutcase and they want to have this confirmed by a doctor.
I can understand that this is humiliateing for you, but if you want to keep your job, you should play along.