KISS -- Keep It Simple, Sam
What is the core set onto which a consensus can be built? Please permit me to get it started.
1) Explosions brought down the three towers.
A. It doesn't matter whether or not any planes hit WTC1 and WTC2 -- it was explosions that brought down all three buildings.
B. It doesn't matter what kind of explosives were used.
C. It doesn't matter whether or not a missile was fired into WTC2 for "shock and awe" effect.
2. ...
What I'm getting at is to avoid the minutia. Stick with a limited set of items that can be proved, and on which all sincere 9/11 truthers can agree.
Assume that there will be government agents who will try to tear a group apart. Accept that some folks are jerks, whose only interest in the 9/11 truth movement is ego inflation.