Well, I think most of the points have already been said...
What could I add, frankly?
---
The purpose of "mono-type" fora doesn't look so uninteresting. As a matter of fact, it's a great tool to decipher the trends working underneath the MBTI theory, or to understand an alien function.
So, I may look odd, but I enjoyed my short stay on the INTJ-f. I learned plenty of things, that's true. Observing, noticing, interacting sometimes...
Hence, the paradox is that "mono-type" fora are only useful when they are able to welcome "foreigners". According to this theory, INTP-c is the least useful mono-type forum, since its existence causes a lot of harm and prejudice against most INTPs (and frankly, they don't deserve this).
On the other hand, INFP-gc and ENTP.org are very pleasant and tolerant places.
---
But let's go back to INTJ-f. I'd say the main problem is not the people who dwell there, it's the administrators who emphasize on their own strict views of what an INTJ should be. They want every INTJs to be pristine, perfect examples of their own biased interpretation of INTJ-ness, and this is absurd.
Their desire to control everything, every possible parameters turned this place into an ubuesque black-and-white nightmare where the use of emoticons becomes a capital crime.
Most INTJs I know aren't like that, they should be allowed to roam free.

Look at their reaction here, on MBTI-c, their revolt is normal, reassuring and justified.
Thus, I have nicknamed INTJ-f as
"The asylum of doctor Tarr and professor Fether" (Cf the short story written by Edgar Allan Poe), where the insane people are actually in charge of the institution.