Anyone have any idea why this is taboo, but virtually every other Biblical subject is not?
Yeah, I think there are several reasons, a couple of which are pretty dominant.
First - western thought does not allow for the existence of demons. As Christians, however, we are taught to believe in the supernatural. So this creates a bit of a knee-jerk revulsion to the subject, particularly since so few people come into contact with demons. There is a limit to what people in our society can swallow, so trying to push deliverance theology on them creates the reaction of, "Okay... well I believe X, X, and X... but now you've just gone too far." And, in some cases, the theology IS taken too far... way, way too far. Which spoils the rest of the barrel.
Which brings me to point two - It's seen as fringe stuff, too far off of the mainstream to be healthy. And the reason is that a lot of times, it is. I've seen some people make some really exaggerated claims that cannot be substantiated or independently validated. This is a real problem, because it saps the credibility of the person making the claim. The problem crops up with faith healers, too - wild claims are made about curing cancer or AIDS, but later investigation shows that the person either never had that disease or that the disease was still there. That is not to say that every single miracle absolutely MUST be medically documented - but people should be bending over backward to gather medical (or in the case of possession, other types) of document-able proof that a miracle has occurred.
Being able to independently verify that something was going on may be harder in cases of demonic possession, because it's not like they can just go to the doctor and get an X-ray. But the effort should still be made, and stuff that seems "too freaky to be real" should never be shared unless there IS some kind of proof of it.
For example, I've heard certain fringe elements talk about cursed objects or tracking devices being removed from people's bodies during exorcism. Okay, so where are the objects? They should be meticulously documented with photos, witness statements, and lab reports. Don't call something a tracking device unless there is proof that it is a tracking device. Likewise, don't call something an animal part unless that has been tested and proven to be exactly that. Ministers, however much experience they may have, are not scientists. I don't find it at all beyond the realm of belief that they could misidentify a piece of bone or a weird fleshy growth as something entirely different. And when people start talking about wild conspiracy theories or really "out there" stuff that no normal person ever encounters, they should not expect anyone - even other Christians - to just take that as fact because we are supposed to have faith.
Another reason this sort of thing turns Christians off is the general attitude that everyone is out to get them! Or whomever is a follower of Christ. Every time someone is mean to us, it must be demonically motivated. Every time we have a hang up - demons. That nasty woman who gave us the evil eye in the grocery line yesterday morning? Well, she must have been a witch who sensed we were Christian, and now she's off casting a spell on us! What other explanation could there possibly be that we got that flat tire yesterday afternoon?
I don't mean this as an attack on you personally, because I know you are a deliverance minister. I'm just trying to explain the wilder stuff out there, because part of the answer to your question is that a lot of this wilder stuff gets lumped into the whole shebang.
Also - one final point. Though there are Christians who are pretty much just sheep that go along with whatever they learn in Sunday School, there are still many out there who are discerning and who know when they are being fed a line. If people go to church and are taught detailed deliverance processes that people have go through, and all sorts of doctrines about legal rights, generational curses, soul ties, and all the other lingo out there... they get the distinct impression that there is a whole lot of fluff and fanfare to casting out demons. They get this impression because they learn that it all has to be done a certain way, have all of the i's dotted and the t's crossed, go through every step and every process or else the nasty demon won't leave or might come back!
... Then they one day meet a real demon, and they learn that facing it down requires absolutely nothing that they were ever taught, only the name of Jesus and their faith in Him.
Well, at that point, that person then knows exactly what a line of bull he/she has been fed throughout the years.
Not to mention all of the Christians who have had "demons" cast out of them when there weren't any demons present... That can very easily leave a bad taste in the mouth.
