zmedelegantdiningroompackanimal:

…there was a notion that they could almost put anything over, that if it was good enough they could sell it to everybody. And I think there was a little hubris in that, because “Check me out, dog. My cast is 60 percent black and my story is all this dysfunction and I’m filmed in Baltimore and…

It’s unclear for me what exactly is the point you want to make, but the fake serial killer plotline made perfect sense to me and was believable troughout because of Poe’s Law. In short it states that a true event/phenomenon can look and sound like a faked one and a fake one can look real.

In this regard, McNulty’s stunt was believable on the grounds that it was unbelievable. Everyone knows that truth can be stranger than fiction, and I found it a brilliant touch that it never occurred to anyone that the serial killer could be a fabrication. It fitted the atmosphere of the series nicely.

Also, I didn’t detect quality drop between S4 and S5, I think S3 was a bit weaker than the other seasons, but S4 was brilliant and S5 was just a bit weaker than S4.