Perhaps I do not understand this all correctly but you are wanting all the denominational forums to have any members enter and tell them how wrong their beliefs are? We surely would lose those members who enjoy their little sections of the site if that were to be allowed.
The bit I don't understand is that if our faith is supposed to be a quest to become more and more Christ-like it rather implies that we need to know more and more what Christ is like. To my mind that means we need to know what is true, not necessarily what our preferred denomination says is true. Since there are so many denominations it stands to reason that at least most of them are wrong about something. Wouldn't you rather discuss your beliefs against someone else's with a view to finding what is true and abandoning anything you believe that runs counter to Scripture, than hide in a little huddle with like-minded people who can join together and pat each other on the back, assuring each other they are right?
If iron sharpens iron, why would we want to sheath the iron? We need rules to make sure that the sharpening is done in love rather than out of a desire to intellectually crush someone else, and with a desire to find truth together. But if we allow little huddles to rest secure in their beliefs and never be challenged, how do we do anybody any favors? It also raises another question of how far away from orthodox Christianity does a group have to be before it does get overtly challenged? Would you create, for example, a Mormon sub-board where Mormon teachings must not be challenged? What about Jehovah's Witnesses? What about universalists? What about Jews, or Muslims, or Hindus? Where does the desire to "contend earnestly for the faith" (as Jude put it) meet the desire to not lose the members who want to avoid having their beliefs tested?
If you are referring to the charistmatic forum, it really is not a denominational one since there are charismatics from all denominations and within that group are differeing beliefs. In there I believe it's fair, without flaming to show how others can be wrong by using scripture.
Charismatics are from all denominations but here it seems we've got another potential can of worms. If denominational forums don't allow the challenging of that denomination's teachings, should the charismatic forum be a denominational forum at all? As you say there are people who identify as charismatic across many denominations, and when it encompasses just about everything from the sense that God can and does do miracles today, to the rather silly excesses of the "name it and claim it" theologies that often bear more resemblance to the New Age movements than Christianity, what (if anything) counts as charismatic teaching that should not be challenged?
For that matter, just as I don't consider it helpful to allow denominations to hide away in little huddles and avoid having anything they believe tested, I don't believe it is helpful to allow charismatic groups to get a free pass on being tested. If anything the charismatic groups warrant more testing, simply because of the increased involvement in what some would call the "spirit world". When concepts like "seeing the spirit realms", "spiritual anointing", "moving in the spirit of the prophetic" etc are thrown around like candy it's worth taking a step back to look at just how (and indeed whether) the teachings align with Scripture.
There does often seem to be a tendency to assume that anything labelled as "Christian" must therefore be from God, and if anything supernatural happens to anyone who even loosely claims the name of Christ the assumption is that "God is at work", when a closer inspection sometimes casts doubt on what, if indeed any, spirit was behind a claimed "miracle".
