Well, because! That's why!
Actually, .... Well, because if you can limit the discussion to the exact words used (say Larry Silverstein's or Woodrow Wilson's, to use two very well-known examples) and limit the conversation to "Did he or did he not say that?", then you can run off waving your Investigate 911 black t-shirt and declaring a victory.
Every time someone says, "Do you have the full quote from Wilson?".... Why you just answer, "La la la la, caaaaannnn't hear you. Did he say it or not? Huh? Did he?" And as soon as he gets you to say, "Look, we already said that we agreed that the quote was correct, but that it is taken out of context and edited." Result?.....
"Ah ha! So, you admit he said it. Thank you!" Then they rush back to ATS or Prison Planet or CIT or PFFFT and tell everyone that they..... "PWND the JREF. I made them admit that Wilson said that, man!"