There were many more reasons for the fall of the Soviets than the arms race. The war in Afghanistan was, however, the final nail in the coffin of the Soviet Union. There is a grain of truth in what he says. The scarey thing is this guy is rich. Richer than any of us and he does know how to handle finance as a weapon. I wouldn't dismiss this strategy out of hand. Whether it is successful or not is another issue. But the first shot across the bow has been fired and maybe our best defense is fiscal responsibility. Arms and military might will never defeat these motherfuckers.
Edit: BTW, don't think bin Laden is stupid. Underestimating your enemy is a tragic error.