Of course, this conspiracy theory sounds interesting and people like to talk about it but we can't judge whole country based on speculations only.
Yes, Bin Laden and some other attackers was from Saudi Arabia and probably some people from this country like terrorist and supporting them but still this is not enough to say that Saudi Arabia is behind this attack.
After all, what will be their motivation, their goal for something like this?
I agree with U. That,s miens someone is background and he helped 9/11 hijackers. And he tried to incline Saudia Arabia.