Part of the reason it's so hard to clear the air with WTC7 is because of the media-perpetuated lies that keep getting airplay. I see this with the evolution debate as well. People want so badly to believe the idea is true (regardless of whether or not it is) that they go on believing things that aren't true, even well after the lie or mistake is corrected (human erabryos having gill slits comes to mind).
With WTC7, there are two glaring things that stand out. One is the Diesel Fuel Scenario. This was given big play back when FEMA was doing their study, even though in their own study, they downplaying the likelyhood of the effect of the fuel in the storage tanks. The NIST final report is summarized to say that standard office furnishings supplied the fuel for the fire that destroyed the structure, and the fires were lit by debris from WTC1 and/or WTC2.
Debris Scenario: the other common falsehood is that debris played a role in the collapse. That is, chunks of building fell on WTC and made it fall down. The NIST report gives no such credence to this idea. I can only assume that it's because the fires were supposedly started by the debris that this secondary idea comes into play. A match started the fire. The match wasn't so heavy, though, as to have calculable mass to contribute to making the house collapse.
I've seen both of this mistaken notions brought forth in this debate thread, and NONE of the official-conspiracy-theory believers will call the others out on it. Why? Because, even though it's a known lie, it supports their case.