dont they have to go along with the president?
Yes they do. But the point I did not adequately make here is that in the past, Bush regime administrators would make the most ridiculous claims (you recall the repeated claims of WMD in Iraq) without presenting even a shred of evidence. The problem was that when Congress was dominated by Republicans they acted as if each of those endless lies were Gospel Truth!
In this particular instance, Negroponte followed the same pattern by making general comments, charges of all kinds, innuendo, but not one bit of proof was presented to verify any of his claims.
Now the real question is, will Congress continue to knuckle under to these endless lies or will they demand actual proof before they decided to take action on Bush's demands?