Hi Alo,
May I first take exception at your offensive statement against a monkey in your first reply to this, but then I do agree with a lot of what you are saying, but with some exceptions.
My feeling is that as far as sciatica and back pain are concerned pain is everything, get rid of the pain and you get rid of the problem. As you mentioned there are plenty of people walking around with large disc prolapses, severe degenerative change and stiff Wikipedia reference-linkfacet joints that are not effecting them in any way. We also scan plenty of people who have severe sciatica and no changes what so ever on the Wikipedia reference-linkMRI film (OK to use this abbreviation?).
My impression is that the pain is often due to a sensitized nerve root which may be due to both mechanical and chemical irritation. Manual techniques often aggravate those sciaticas which are "chemical" in origin and these respond best to pure pain control. Are the effects of manipulation purely mechanical? There are schools of thought that suggest manipulations greatest effect is pain modulation.
What I would suggest is do anything that you can to get rid of the pain to allow the person to return to activity. This can be anything from manipulation, medication, advice (yes, just talking sometimes helps best), exercises, acupuncture and if you live in the dark ages use electrotherapy. Usually a combination tailored to the individual works best (treat the person not the condition), and that surely is what the initial assessment is all about.